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When the robotic lander Odysseus last month became the first American-built spacecraft to touch down on the moon in more than 50 years, it toppled over at an angle. That limited the amount of science it could do at the lunar surface, because its antennas and solar panels were not pointed in the correct directions.

Just a month earlier, another spacecraft, the Smart Lander for Investigating Moon, or SLIM, sent by the Japanese space agency, had also tipped during landing, ending up on its head.

Why is there a sudden epidemic of spacecraft rolling on the moon like Olympic gymnasts performing floor routines? Is it really that difficult to land upright there?

On the internet and elsewhere, people pointed to the height of the Odysseus lander — 14 feet from the bottom of the landing feet to the solar arrays at the top — as a contributing factor for its off-kilter touchdown.

Had Intuitive Machines, the maker of Odysseus, made an obvious error in building the spacecraft that way?

The company’s officials provide an engineering rationale for the tall, skinny design, but those internet commenters do have a point.

Something tall falls over more easily than an object that is short and squat. And on the moon, where the pull of gravity is just one-sixth as strong as on Earth, the propensity to tip over is even greater.

This is not a new realization. A half-century ago, Apollo astronauts had firsthand experience as they hopped around on the moon, and sometimes tumbled to the ground.

On the social media site X last week, Philip Metzger, a former NASA engineer who is now a planetary scientist at the University of Central Florida, explained the math and the physics of why it is more difficult to remain standing on the moon.

“I’ve actually gone through calculations, and it’s really scary,” Dr. Metzger said. “The side motion that can tip a lander of that size is only a few meters per second in lunar gravity.” (One meter per second is, in everyday American units, a bit more than two miles per hour.)

There are two parts to this question of stability.

The first is static stability. If something is standing at much of an angle, it will fall over if the center of gravity is to the outside of the landing legs.

Here, it turns out the maximum angle of leaning is the same on Earth as it is on the moon. It would be the same on any world, large or small, because gravity cancels out of the equation.

However, the answer changes if the spacecraft is still moving. Odysseus was supposed to land vertically with zero horizontal velocity, but because of problems with the navigation system, it was still moving sideways when it hit the ground.

“Intuition that’s based on Earth is now a liability,” Dr. Metzger said.

He gave the example of trying to push over the refrigerator in your kitchen. “It’s so heavy that a slight push is not going to push it over,” Dr. Metzger said.

But you replace it with a piece of Styrofoam in the shape of a refrigerator, mimicking the weight of a real refrigerator in lunar gravity, “then a very light push will push it over,” Dr. Metzger said.

Assuming the spacecraft remains in one piece, it would rotate at the point of contact where the landing foot touches the ground.

Dr. Metzger’s calculations suggested that for a spacecraft like Odysseus, the landing legs need to be splayed about two and a half times as wide on the moon as on the Earth to counteract the same amount of sideways motion.

If, for example, six feet wide were enough for landing on Earth at the maximum horizontal speed, then the legs would have to be 15 feet apart in order not to tip on the moon at the same sideways speed.

For simplicity of design, the landing legs of Odysseus did not fold up, and the diameter of the SpaceX Falcon 9 rocket that lifted it to space limited how wide the landing legs could spread out.

“So, on the moon, you have to design to keep the sideways velocities very low at touchdown, much lower than you would if landing the vehicle in Earth’s gravity,” Dr. Metzger wrote on X.

I too wondered about the shape of the lander when I visited the Intuitive Machines headquarters and factory in Houston in February last year.

“Why so tall?” I asked.

Steve Altemus, the chief executive of Intuitive Machines, replied that it had to do with the tanks that hold the spacecraft’s liquid methane and liquid oxygen propellants.

The methane weighs twice as much as the oxygen, so if the methane tank were placed next to the oxygen tank, the lander would have been unbalanced. Instead, the two tanks were stacked on top of each other.

“That created the height,” Mr. Altemus said.

Scott Manley, who provides commentary about rockets on X and YouTube, noted that Mr. Altemus had led the development of a shorter, squatter lander when he was at NASA a decade ago.

That test lander, named Morpheus, also used methane and oxygen propellants, but the tanks were configured in pairs to keep the weight in balance. It was never meant to fly to space.

In an interview, Mr. Manley said that design would have worked for the Intuitive Machines lander as well but would have made the spacecraft heavier and more complex.

If the spacecraft needed two methane tanks and two oxygen tanks, the spacecraft structure would have needed to be bigger and heavier. The tanks would have been heavier too.

“You’ve got more surface area, so that’s more surface to insulate,” Mr. Manley said. He added that it would also have needed “more plumbing and more valves, more things to go wrong.”

For the landing site in the south pole region, the height of Odysseus offered another advantage. At the bottom of the moon, sunlight shines at low angles, producing long shadows. If Odysseus had remained upright, the solar arrays at the top of the spacecraft would have remained out of shadows longer, generating more power for the mission.

During the visit to Intuitive Machines, Tim Crain, the company’s chief technology officer, said the spacecraft had been designed to stay upright when landing even on a slope of 10 degrees or more. The navigation software was programmed to look for a spot where the slope was five degrees or less.

Because the laser instruments on Odysseus for measuring altitude were not working during descent, the spacecraft landed faster than planned on a 12-degree slope. That exceeded its design limits. Odysseus skidded along the surface, broke one of its six legs and tipped to its side.

If the laser instruments had been operating, “We would have nailed the landing,” Mr. Altemus said during a news conference last week

The same concerns will apply for SpaceX’s humongous Starship, which will take two NASA astronauts to the moon’s surface as soon as 2026.

Starship, as tall as a 16-story building, will have to come down perfectly vertically and avoid significant slopes. But those should be solvable engineering challenges, Dr. Metzger said.

“It removes some of the margin of error in your dynamic stability, but it doesn’t remove all the margin of error,” Dr. Metzger said of a tall lander. “The amount of margin that you have left is manageable as long as your other systems on the spacecraft are functioning.”

Since introducing the App Store in 2008, Apple has run it largely the same way across 175 countries, right down to the 30 percent commission it has collected on every app sold.

The company calls the result an economic miracle. The store has generated more than $1 trillion in sales, helped create more than seven million jobs and delivered Apple billions of dollars in annual profits.

But as the App Store approaches its 16th anniversary, a patchwork of local rules are upending Apple’s authority over it.

On Thursday, European Union regulators will begin enforcing the Digital Markets Act, a 2022 law that requires Apple to open iPhones in the bloc to competing app marketplaces and alternative payment systems for in-app sales.

The changes follow similar demands in South Korea and the United States, where Apple has been forced to allow alternative payment processors. Similar concessions are being discussed in Britain, Japan and Australia.

The rules are fracturing what was once a single store into a jumble of digital shops across national borders. The once uniform experience of shopping for software on an iPhone now differs, depending on where people live.

“The App Store is being completely splintered,” said Eric Seufert, who invests in app makers and runs Mobile Dev Memo, a blog about the app economy. “The approach to complying is pretty similar: ‘Let’s cut the fee a little bit.’ But it’s a pain.”

Apple has worked hard to adapt to the shifting regulatory landscape. An Apple spokesman said the company had spent months talking with the European Commission about the Digital Markets Act and hosted meetings with developers as it developed plans to change the App Store while minimizing the risks of malware, fraud and scams on iPhones.

Apple says its control over the App Store is critical to the safety and quality of the apps it distributes. The company has stopped short of abandoning the 30 percent commission. But over time, it has made some concessions to developers and regulators by reducing the commissions that smaller app makers pay and allowing developers to link out to their websites to charge users directly for subscriptions.

The changes are expected to pinch Apple’s sales and cut into profits. Last year, the App Store generated an estimated $24.12 billion in revenue, according to Bernstein Research.

When the App Store first appeared, Steve Jobs, Apple’s co-founder, said the fee was a “great deal” because it allowed every developer — big or small — to deliver software to every single iPhone. But for years, Apple’s fees have been a point of frustration for developers. Over time, regulators began to listen to those complaints.

In 2019, Spotify filed a complaint against Apple in Europe, accusing it of anticompetitive practices because it prevented streaming music services from advertising where and how users could subscribe to their app. A year later, Epic Games, the maker of Fortnite, filed a lawsuit in U.S. federal court accusing Apple of violating antitrust laws by forcing developers to use its payment system.

The complaints galvanized developers around the world to begin lobbying for changes to the app economy. In 2021, South Korean lawmakers were among the first to respond by passing legislation to force app store operators to allow alternative payment systems. Apple relaxed its requirement that developers use its in-app payment service, but said developers who used alternative services would owe Apple a 26 percent commission on sales.

Developers have argued that the new commission rate is the same as the 30 percent rate after credit card processing fees are added. Their criticisms have resonated with regulators in South Korea, who said Apple’s plan undermined the law’s goal. The country’s telecommunications regulator said it might fine Apple $15.4 million for “unfair practices.”

Apple said it disagreed with the conclusion of regulators in South Korea and believed that its changes complied with the law.

The company took a similar approach in the United States. During the Epic Games lawsuit, Tim Cook, the chief executive of Apple, said that being forced to offer alternative payment systems “would be a mess.”

“We would have to come up with another system to invoice developers,” he said, adding that Apple would still charge a commission.

The federal judge in the case ruled in 2021 that Apple needed to allow alternative payments in the United States. Apple has complied much as it did in South Korea, except it said developers that used alternatives owed a 27 percent commission.

“Clearly, it’s window dressing,” said Colin Kass, an antitrust lawyer with Proskauer Rose who has no connection to the case. “Does it satisfy the court? Maybe.”

Apple said that the judge had upheld its right to charge a commission, and that its solution fulfilled the judge’s request to allow out-of-app purchases. Epic said it planned to file a motion challenging the 27 percent fee and asking the court to intervene.

In 2022, the European Union passed the Digital Markets Act to introduce competition to the App Store on iPhones, among other changes. Apple had two years to comply.

The company’s engineers have spent thousands of hours creating more than 600 new software tools for developers. In January, the company introduced those tools and outlined three options for app makers in the European Union, home to roughly 450 million people.

Under Apple’s plan, developers could stick with the status quo App Store system and pay up to a 30 percent commission on sales. They could reduce their commission to 17 percent while adding a new 50-euro-cent charge on every download above one million annually. Or they could avoid Apple’s commission by selling through a competing app store while still paying the download fee.

Apple said the plan complied with the law and meant that 99 percent of developers in the European Union would reduce or maintain the fees they owed.

But app makers said the plan violated the letter and spirit of the law. Under the new rules, a tech giant like Apple is supposed to allow app makers to sell subscriptions and services outside their apps “free of charge,” said Damien Geradin, a European antitrust lawyer who is advising app developers. He said Apple’s 50-euro-cent fee and 17 percent commission broke that part of the law.

European regulators won’t weigh in on Apple’s proposal until after the effective date on Thursday. Should they open a formal investigation, it could set up a lengthy legal battle that could force Apple to change or risk fines up to 10 percent of its global annual revenue, which was nearly $400 billion last year.

Mr. Geradin said Apple was unlikely to succeed but, in the interim, could continue collecting commissions.

“It’s part of their tactics,” he said.

In a blow to government efforts to combat money laundering, a federal court has ruled that the Treasury Department cannot require some small businesses to report personal details about their owners.

Under a section of a 2020 law that took effect Jan. 1, small businesses must share details about their so-called beneficial owners, individuals who hold financial stakes in a company or have significant power over their business decisions. The law, the Corporate Transparency Act, passed with bipartisan support in Congress and was intended to help the Treasury Department’s financial-crimes division identify money launderers who hide behind shell corporations.

But in a ruling issued late Friday, Judge Liles C. Burke of the U.S. District Court in Huntsville, Ala., sided with critics of the law. They argue that asking a company’s owners to present personal data — names, addresses and copies of their identification documents — was a case of congressional overreach, however well intended.

“Congress sometimes enacts smart laws that violate the Constitution,” Judge Burke wrote in a 53-page filing. “This case, which concerns the constitutionality of the Corporate Transparency Act, illustrates that principle.”

Judge Burke’s ruling prevented the department from enforcing the ownership reporting requirements on the plaintiff in the Alabama case, the National Small Business Association, a nonprofit trade group that represents more than 65,000 member companies.

Lawyers who have followed the Alabama case said over the weekend that they expected the government to quickly request that the injunction be paused, either by Judge Burke or the 11th Circuit Court of Appeals in Atlanta, or both. The Justice Department will almost certainly appeal the Alabama case to the circuit court, the lawyers said.

Morgan Finkelstein, a Treasury Department spokeswoman, said her agency was “complying with the court’s injunction.” She referred further questions to the Justice Department, which declined to comment.

As lawyers and transparency experts pored over Judge Burke’s opinion, the immediate impact of the ruling for the universe of small businesses in the United States, which the government estimates at 33 million, was not entirely clear.

Companies were given a year to comply with the reporting requirements as they pertained to the year 2023, so the data is not even due until the end of 2024. And Judge Burke’s ruling, read narrowly, does not apply to small businesses that are not members of the trade organization that brought the Alabama suit, meaning that most of the companies affected by the mandate must still comply.

“This has only made it more complicated for a lot of my clients,” said Angela I. Gamalski, who advises large and small corporations on compliance and regulatory matters at the law firm Honigman LLP in Ann Arbor, Mich. Ms. Gamalski said she planned to wait until the summer to dig into the reporting requirements and what they meant for her clients, given that the filing deadline is not until December and the enforcement of the law seemed to be in flux.

Proponents for greater transparency decried the ruling.

“This is an aberrant decision issued by a lone district judge in Alabama, based on an extraordinarily narrow view of Congress’s constitutional powers that is unsupported by precedent,” said Senator Sheldon Whitehouse, the Rhode Island Democrat who is one of the law’s supporters. “I would urge the government to appeal quickly to correct the erroneous decision and ensure the law’s transparency requirements can be fully and uniformly implemented.”

The hiking trail to Middleham Falls on the Caribbean island of Dominica is all wet leaves, slippery black stones and steps formed by tree roots. It could be a path in Middle-earth, shrouded, shadowy and green, fit for hobbits and fairies. Where sunlight pierced the canopy, rainbows formed in the mist, almost close enough to poke. Here and there, hummingbirds drew nectar from huge blossoms.

The goal on that January day: a 200-foot forest cascade filling and refilling little pools on the valley floor, where I could — as one does in the secret hot pools and isolated waterfalls of Dominica — shed my clothes, slip into water and commune with the hummingbirds like a fairy queen.

Dominica, 29 miles long and, at its widest, 16 miles across, is one of the wildest Caribbean islands. A former British colony, it lies in the eastern Caribbean between Guadeloupe and Martinique. Many travelers base themselves in its capital, Roseau. Thanks in part to its rugged topography, bisected by a volcanic mountain range with Jurassic-looking conical peaks, the island was the last Caribbean island to be colonized by Europeans.

Even today, getting to, and around, this tropical bastion, a New York Times 52 Places to Go in 2024 pick, takes a taste for adventure, patience and a strong stomach. There are few direct flights from the United States and once one lands, the journey is not over. Driving around the island in a rental car — to lodging, hikes and snorkeling sites, and to visit local experts — usually involved long, queasy rides on narrow concrete ribbons hacked through mountain jungle in the last century by pickax, shovel and wheelbarrow.

A place of ups and downs

The island is a big draw for hikers who enjoy a challenge: Walking almost anywhere beyond the coast involves going up or down. Boiling Lake, a flooded volcanic fumarole and popular attraction, lies at the end of a strenuous three-hour trek from the village of Laudat. The government is building a cable car, scheduled to be completed late this year, that will whisk visitors from near Laudat to the lake in just 15 minutes.

Even after the cable car opens, hikers will be able to choose from a network of mountain paths, including the 115-mile Waitukubuli National Trail, which traverses the entire island in 14 stages and takes six days to complete. (Waitukubuli is the Indigenous name for the island.)

Dominica, which brands itself as the Nature Island, has tried to protect its wild side. The route to Middleham Falls is one of dozens of marked and unmarked hiking trails around the volcanic 17,000-acre Morne Trois Pitons National Park, a UNESCO World Heritage site.

Offshore, the government has opened a new reserve for sperm whales, complementing a marine reserve that protects coral and reef animals. And locals have joined the effort. For the past year, Simon Walsh, who runs Nature Island Dive, and his fellow divers have been painstakingly applying an amoxicillin caulk to corals showing signs of stony coral tissue loss disease, which has been spreading around the Caribbean for about a decade.

My travel companion and I snorkeled in the reef near the dive shop at Bubble Beach (so named for the tiny bubbles from volcanic springs rising from the sand), and easily spotted the white medicine outlining the disease-damaged spots.

Mr. Walsh had plans to save some specimens from coral bleaching, a devastating phenomenon linked to climate change, by transferring some into tanks to protect them from another summer of record-high water temperatures. But a tragic turn of events has put that effort in jeopardy.

Mr. Walsh has operated both coral rescue projects through a nonprofit called REZDM. The organization, formed after Hurricane Maria ravaged the island in 2017, received much of its funding from Daniel Langlois, a Canadian philanthropist who had built an off-the-grid resort near the town of Soufriere. Last November, Mr. Langlois and his partner were killed, a rare crime on a largely safe island. The police have charged the American owner of a neighboring estate, who had reportedly been feuding with Mr. Langlois over the use of a road through his property, and a Florida man, with murder. Mr. Walsh doesn’t know whether the projects will continue to receive funding.

A garden everywhere you go

Dominica receives up to 250 inches of rain annually, feeding crystal streams, waterfalls and thousands of acres of lush forest. Hurricanes like the Category 5 storm Maria have ravaged and reshaped the island repeatedly over the centuries.

The upside to all that precipitation is the Edenic ecosystem. Much of the island feels like an untamed garden. Spectacular blossoms peek from profuse green almost everywhere. Birds of paradise and other dazzling flowers sprout like weeds. Grab a handful of tall grass on a roadside, crush it and inhale lemongrass. Pluck a berry from a tree and it could be one of a half dozen types of cherry. Twenty-pound globes of jackfruit, rock hard and encased in bright green, elephant-skin-like hide, dangle from branches.

Fantastic private gardens also cultivate many of these wild plants. Jungle Bay Resort in Soufriere claims to have 75 different tropical fruit trees in its garden, a number we doubted until its owner, Sam Raphael, marched us around for 45 minutes, ticking off and letting us taste dozens of species. On the edge of Roseau, the entrance to the 40-acre Dominica Botanic Garden, established in 1889, is marked by a tree whose branches, leafless when I visited, sprout large, fluffy yellow flowers that resemble peonies — a great beauty with a whimsical name, buttercup tree.

At Papillote Wilderness Retreat, we were able to spend the night in a garden. Situated a few hundred yards below Trafalgar Falls, a double waterfall, Papillote predates many of the other eco-friendly establishments on the island. Its owner, Anne Jno Baptiste, came from New York in 1961 and bought the land, including its 40-foot waterfall and steaming volcanic springs, to create a botanical garden. Now 94, she is modest about her garden and philosophical about the challenges. She has survived five major hurricanes. “We’ve had some landslides,” she says. “You see, everything changes. Life is like that. You just pick up the pieces.”

The retreat is a charmingly ramshackle landmark with a few simple rooms. Steps wind underneath Day-Glo orange and pink flowers and giant ferns to a secret garden. Twice daily, we wandered down and found out what standing under a 40-foot waterfall does for sore shoulders, then plunged into a hot pool for a long soak. Our accommodations also had a perpetually bubbling tub of hot volcanic water inside the bathroom. Our room went for $130 a night (as with many places on the island, we paid in U.S. dollars, worth about 2.7 Eastern Caribbean dollars, the local currency).

Ambitious plans and rising fears

The historian Lennox Honychurch is among the islanders who worry about the government’s plans to expand and modernize tourist infrastructure. Like many Caribbean islands, Dominica is conflicted between the demands of snowbirds with money who want luxury accommodations and easier air access and environmentalists and advocates of a scaled-down, sustainable local economy who fear losing the “nature” part of their island.

Besides the cable car to Boiling Lake, builders are working on a large, new international airport, about a one-hour drive from the capital, which is expected to be completed by 2027, according to Samuel Johnson, chief executive of the International Airport Development Company of Dominica. And the government is planning to welcome half a million cruise ship visitors annually. “Their dream is to have big, glitzy hotels with marble lobbies,” Mr. Honychurch said.

Denise Charles-Pemberton, the tourism minister, didn’t deny that she wanted more tourists and more direct flights. But she insisted that the government was also focused on environmental protection. “We want our visitors to be responsible, to understand that our vision is to be a great destination, and when they come they have to be respectful to nature,” she said.

For now, upscale food and lodging are available, but they’re not the norm. A few high-end resorts serve good meals — but at prices that would raise eyebrows even in Miami or New York. The best food options in terms of taste, price and ambience are roadside shacks and kiosks with outdoor tables.

In Soufriere, we bought plates of takeout chicken stew for about $5.90 each at the shed-size, pastel blue Teachers Place. We ate stewed fish ($15) on the porch of the River Rock Cafe and Bar, with stupendous views of the Roseau River tumbling through the forest. The best meal we had was chicken roti (about $4.80) at Vado’s HotSpot, a bright red roadside cargo container.

Soaking in the stardust

One rainy afternoon after a day of hiking and snorkeling, we decided to check out the volcanic pools at Ti Kwen Glo Cho (patois for Coin de l’Eau Chaude, or “hot water corner” in French), in a riverine slot between two towering walls of green. For about $18.50 for the two of us, we entered and found our way to a series of steaming cement-lined pools nestled among low palms, ferns and birds of paradise.

We joined a gaggle of other international visitors in the largest pool, and soon we were all cooking together like a global soup. We sat in the boil until we could stand it no longer. Steam rose from bright red bodies draped on the pool’s edge, cooled by tiny raindrops. Drowsy, blissed out, practically narcotized, we lay supine as the sun dropped behind the mountain, peepers started clamoring in the shadows and the sky turned starry black. “We are stardust,” I thought, recalling the lyrics of the Joni Mitchell song “Woodstock,” as I looked to the heavens.

Barely a day later, back in the cold, gray winter of the Northeast, surrounded by traffic, fast food and A.T.M.s spitting sheaves of dollars, I couldn’t help thinking back to that beguiling dusk at Ti Kwen Glo Cho and finishing the verse of the song: “And we’ve got to get ourselves back to the garden.”

Follow New York Times Travel on Instagram and sign up for our weekly Travel Dispatch newsletter to get expert tips on traveling smarter and inspiration for your next vacation. Dreaming up a future getaway or just armchair traveling? Check out our 52 Places to Go in 2024.

Nikki Haley suggested Sunday that she might no longer feel bound by the pledge she made, in order to participate in the Republican primary debates last year, to support the party’s eventual nominee — opening up the possibility that she would not endorse former President Donald J. Trump if he wins the nomination, as he seems increasingly likely to do.

At the same time, she repeated her past assertions that President Biden was a worse option than Mr. Trump, and said that she did not want to engage in “what ifs” or “hypotheticals” premised on her losing the primary. At no point did she rule out endorsing Mr. Trump, even as she said that he had allowed “lawlessness” on Jan. 6 and that she didn’t know whether he would follow the Constitution as president.

The exchange, on NBC News’s “Meet the Press,” began when the host, Kristen Welker, asked whether Ms. Haley had taken the prospect of endorsing Mr. Trump “off the table.”

Ms. Haley hedged, saying, “It’s not anything I think about,” adding: “If you talk about an endorsement, you’re talking about a loss. I don’t think like that.”

After an extended back-and-forth, she described the Republican National Committee pledge she signed last year and said, referring to Mr. Trump’s endorsement of Lara Trump, who is married to his son, Eric, to be a party co-chair, replacing the outgoing chairwoman, Ronna McDaniel: “The R.N.C. is now not the same R.N.C. Now it’s Trump’s daughter-in-law.”

“I think I’ll make what decision I want to make,” she added. “But that’s not something I’m thinking about. And I think that while y’all think about that, I’m looking at the fact that we had thousands of people in Virginia, we’re headed to North Carolina, we’re going to continue to go to Vermont and Maine and all these states to go and show people that there is a path forward.”

A lot of climate discussion revolves around time. Lines rise across charts predicting the next century. Scientists set deadlines for the coming decades. Each month seems to bring news of a new heat record. The sense that time is running out can be heady.

As the Earth warms, natural wonders — coral reefs, glaciers, archipelagos — are at risk of damage and disappearance. This has motivated some travelers to engage in “last-chance tourism,” visiting places threatened by climate change before it’s too late.

“For thousands of years, humans have raced to be the first to scale a peak, cross a frontier, or document a new species or landscape,” Paige McClanahan writes in a piece for The Times. “Now, in some cases, we’re racing to be the last.”

A vanishing glacier

One such destination is the Mer de Glace, the largest glacier in the French Alps, where thousands of people go each year to ski. (Early tourists included Mary Shelley and Mark Twain.)

The glacier, like many others, is melting rapidly. A new, higher lift opened recently to stay closer to the retreating ice. And a study published in the journal Science last year found that around half of the world’s glaciers will have melted by the end of this century, even if nations stick to the goals of the Paris climate agreement.

“For someone who doesn’t know how it used to be, it’s a beautiful scene,” a visitor to the glacier told Paige. “But when you know the difference, it really is sad.”

Pros and cons

There is some evidence that visiting an ecosystem threatened by climate change could lead people to become more aware of their impact on the environment.

In a 2020 survey conducted by researchers at the Mer de Glace, 80 percent of visitors said that they would try to learn more about how to protect the environment, and 77 percent said they would reduce their water and energy consumption.

Some tourist spots have leaned into education. In Peru, officials renamed a trek to the Pastoruri glacier “La Ruta del Cambio Climático,” or “The Route of Climate Change.” And at the Mer de Glace, an exhibit about climate change — called the Glaciorium — is set to open later this year.

There are some, however, who question of the value of last-chance tourism. Visiting fragile environments can do more harm than good.

Some people travel to Antarctica because they fear it is being destroyed. But, as Sara Clemence highlighted in a piece in The Atlantic last year, travel there requires a lot of fuel, while visitors can introduce disease and damage wildlife. And research by Karla Boluk, an academic from the University of Waterloo, found that a majority of last-chance tourists to two sites in Canada were unwilling to pay extra to offset the carbon footprint of their trip.

“There’s an ethical paradox of last-chance tourism,” Boluk told The Times, “and it involves the moral question of whether travelers acknowledge and respond to the harm they promote.”

Read Paige’s full story here.

THE LATEST NEWS

2024 Election

THE SUNDAY DEBATE

Should Michigan’s protest vote worry Biden?

Yes. That 100,000 Michigan voters vented their discontent with Biden, many over his handling of Israel’s invasion of Gaza, is a problem for him. “The Biden campaign has to deal with how the president’s policy could impact his re-election effort,” USA Today’s Sara Pequeño writes.

No. There are more moderates who agree with Biden’s policies than there are progressives who disagree with him. “It would be a mistake to think that shifting his policy to the left would be a net gain for him,” John Halpin writes for CNN.

Hidden history: Alderney, a windswept island in the English Channel, feels like a remote haven. During World War II, it was a site of Nazi atrocities.

Thank you very much: As a boy in Pakistan, Airaj Jilani idolized Elvis. Decades later in the U.S., he still has his passion — and his impeccable impersonation.

Vows: Their corporate speak turned into a language of love.

Lives Lived: Nancy Wallace helped transform the Bronx River from a watery graveyard for automobiles and appliances into an urban greenbelt for New York City. She died at 93.

THE NEW YORK TIMES MAGAZINE

The A.I. industry continues to boom, and to poke at our anxieties. In late 2022, I spoke with the pioneering researcher Yejin Choi, who works on developing common sense and ethical reasoning in A.I.

Can you explain what “common sense” means in the context of teaching it to A.I.?

It’s the unspoken, implicit knowledge that you and I have. It’s so obvious that we often don’t talk about it. You and I know birds can fly, and we know penguins generally cannot. So A.I. researchers thought, we can code this up: Birds usually fly, except for penguins. But in fact, newborn baby birds cannot fly, birds covered in oil cannot fly. The point being, exceptions are not exceptional, and you and I can think of them even though nobody told us. It’s not so easy for A.I.

What’s most exciting to you right now about your work in A.I.?

I’m excited about value pluralism. Another way to put it is that there’s no universal truth. A lot of people feel uncomfortable about this. As scientists, we’re trained to be very precise and strive for one truth. Now I’m thinking, well, there’s no universal truth — can birds fly or not? Moral rules: There must be some moral truth. Don’t kill people, for example. But what if it’s a mercy killing? Then what?

How could you possibly teach A.I. to make moral decisions when almost every rule or truth has exceptions?

A.I. should learn exactly that: There are cases that are more clean-cut, and then there are cases that are more discretionary. Instead of making binary, clean-cut decisions, it should sometimes make decisions based on This looks really bad. Or you have your position, but it understands that, well, half the country thinks otherwise.

Read more of the interview here.

BOOKS

New fiction: “Wandering Stars,” the follow-up to Tommy Orange’s “There There,” follows the descendants of a massacre on Native Americans over a century and a half. Our review calls it a towering achievement.

Our editors’ picks: In “The Mysterious Case of the Alperton Angels,” readers sift through texts, emails and more to discover the story behind a series of occult deaths.

Times best sellers: “The Chaos Agent,” the 13th book in Mark Greaney’s Gray Man series, is new this week on the hardcover fiction best-seller list.

THE MORNING RECOMMENDS …

Check in on your emotional well-being.

Clean your dog’s bed.

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THE WEEK AHEAD

What to Watch For

• North Dakota holds Republican caucuses tomorrow.

• Then it’s Super Tuesday. Sixteen states have primary elections or caucuses, including California, where Representatives Katie Porter and Adam Schiff are competing for a Senate seat.

• Biden will make the State of the Union address on Thursday.

• International Women’s Day is Friday.

• Congress’s deadline to avert a government shutdown is Friday.

• Trump is scheduled to host Hungary’s prime minister, Viktor Orban, at Mar-a-Lago on Friday.

What to Cook This Week

In this week’s Five Weeknight Dishes newsletter, Emily Weinstein suggests making Eric Kim’s five-ingredient peanut butter noodles, which she calls “a Parmesan-tossed classic in the making.” Her other suggestions include an orange-glazed baked salmon, a one-pan crispy chicken and chickpeas and a cheesy and spicy black bean bake.

NOW TIME TO PLAY

Widespread concerns about President Biden’s age pose a deepening threat to his re-election bid, with a majority of voters who supported him in 2020 now saying he is too old to lead the country effectively, according to a new poll by The New York Times and Siena College.

The survey pointed to a fundamental shift in how voters who backed Mr. Biden four years ago have come to see him. A striking 61 percent said they thought he was “just too old” to be an effective president.

A sizable share was even more worried: Nineteen percent of those who voted for Mr. Biden in 2020, and 13 percent of those who said they would back him in November, said the 81-year-old president’s age was such a problem that he was no longer capable of handling the job.

The misgivings about Mr. Biden’s age cut across generations, gender, race and education, underscoring the president’s failure to dispel both concerns within his own party and Republican attacks painting him as senile. Seventy-three percent of all registered voters said he was too old to be effective, and 45 percent expressed a belief that he could not do the job.

This unease, which has long surfaced in polls and in quiet conversations with Democratic officials, appears to be growing as Mr. Biden moves toward formally capturing his party’s nomination. The poll was conducted more than two weeks after scrutiny of his age intensified in early February, when a special counsel described him in a report as a “well-meaning, elderly man with a poor memory” and “diminished faculties in advancing age.”

Previous polling suggests that voters’ reservations about Mr. Biden’s age have grown over time. In six top battleground states surveyed in October, 55 percent of those who voted for him in 2020 said they believed he was too old to be an effective president, a sharp increase from the 16 percent of Democrats who shared that concern in a slightly different set of swing states in 2020.

Voters have not expressed the same anxieties about Donald J. Trump, who at 77 is just four years Mr. Biden’s junior. Their likely rematch would make them the oldest presidential nominees in history.

If re-elected, Mr. Biden would beat his own record as the oldest sitting president, while Mr. Trump would be the second-oldest if he won. Mr. Trump would be 82 at the end of the term, and Mr. Biden would be 86.

Otto Abad, 50, an independent voter in Scott, La., said he voted for Mr. Biden in 2020 but planned to flip his support to Mr. Trump if they faced off again. Last time, he wanted a less divisive figure in the White House after the chaos of the Trump administration. Now, he worries that Mr. Biden is not quite up for a second term.

“If he was in this sort of mental shape, I didn’t realize back then,” Mr. Abad said. “He’s aged a lot. With the exception of Trump, every president seems to age a lot during their presidency.”

He added: “Trump, one of the few things I would say good about him, is that nothing seems to bother him. He seems like he’s in the same mental shape he was 10 years ago, 12 years ago, 15 years ago. He’s like a cockroach.”

Mr. Abad is far from alone. Just 15 percent of voters who supported Mr. Trump in 2020 said they thought he was now too old to be an effective president, and 42 percent of all voters said the same — a much lower share than for Mr. Biden. Polling from the 2020 race indicates that the share of voters who believe Mr. Trump is too old has also increased over the past four years, but not as drastically as for Mr. Biden.

In the most recent Times survey, 19 percent of all voters said Mr. Trump’s age was such a problem that he was not capable of handling the presidency. And in a sign of Republicans’ far greater confidence in their likely nominee, less than 1 percent of voters who backed Mr. Trump in 2020 said his age made him incapable.

Mr. Biden and his allies have rejected anxieties about his age and mental acuity as unfair and inaccurate. His campaign says its coalition will again rally around the president once it fully recognizes that Mr. Trump could win back the White House. It also argues that Mr. Biden faced age concerns in 2020 and still won.

Yet Mr. Biden is now four years older, and it may be impossible to completely reassure voters about his age given the inexorable march of time. The poll indicates that the worries about him are not only pernicious but also now intertwined with how many voters view him.

Calvin Nurjadin, a Democrat in Cedar Park, Texas, who plans to support Mr. Biden in November, said he was unconvinced by politicians in his party who have publicly played up their direct observations of Mr. Biden’s mental sharpness.

“You’ve just kind of seen the clips of, you know, he’s having memories onstage and, you know, during debate and discussion where he kind of freezes up a lot,” said Mr. Nurjadin, who does data entry work. “Him being sharp and fit is not very convincing.”

Even though the country is bitterly divided and Republican voters have overwhelmingly negative views of Mr. Biden’s age, Democrats do not appear to be more worried about the effects of time on Mr. Trump than on Mr. Biden. Similar shares of Democrats said each man was too old to be effective.

The poll tried to understand in greater depth how voters thought about Mr. Biden’s and Mr. Trump’s abilities. The survey first asked if each man was too old to be effective. Voters who said yes were asked a follow-up question about whether that age was such a problem that Mr. Biden or Mr. Trump was not capable of handling the job, a stronger measure that prompted voters to consider the candidate’s basic fitness for office.

Shermaine Elmore, 44, a small-business owner in Baltimore, voted for Mr. Biden four years ago, backing the Democratic candidate as he had in previous elections.

But he said he had made more money under Mr. Trump, blaming inflation and gas prices for his losses during the Biden administration. He planned to vote for Mr. Trump this fall.

Of Mr. Biden, he said: “I don’t think he’s in the best health to make a decision if the country needs the president to make a decision.”

Samuel Friday, 28, a database administrator and a Democrat in Goose Creek, S.C., said he planned to vote for Mr. Biden but had some apprehension about whether the president would survive a second term.

“In terms of his health, I think people have come out and said that he’s healthy as can be, which is always positive,” he said. “But when you get to a certain age, there is the higher risk that the president could die in office. And I’m not sure that Kamala Harris would be the choice that I would want in the presidency.”

Indeed, the vice president is not seen any more positively than Mr. Biden. Only 36 percent of all voters said they had a favorable view of Ms. Harris.

About two-thirds of those who voted for Mr. Biden in 2020 expressed a positive view of Ms. Harris, nearly the same as for the president. And in a head-to-head contest with Mr. Trump, Ms. Harris did not fare any better than Mr. Biden, losing by six percentage points.

While Democrats are still divided, they also seem to be slowly unifying behind Mr. Biden’s bid. Forty-five percent of Democratic primary voters said he should not be their party’s nominee, compared with 50 percent who expressed that view in July.

Margaret Stewart, a retiree from Westland, Mich., said she would have preferred a younger nominee but was not particularly bothered by Mr. Biden’s age. The president, she said, sometimes makes verbal missteps when he is stressed but is mentally fit to serve as president.

“Some of the little flubs he had, one, he’s had those forever,” she said, “and I honestly think his memory is better than mine when I was in my 40s.” She added, “He’s not senile.”

Overall, voters generally express warmer views about Mr. Biden than Mr. Trump. Fifty-one percent of registered voters said the president had the personality and temperament to be president, compared with 41 percent who said the same about Mr. Trump. Among Republicans, 27 percent said Mr. Trump lacked those traits, while 14 percent of Democrats said the same of Mr. Biden.

Brian Wells, 35, a lawyer from Huntsville, Ala., described himself as a reluctant supporter of Mr. Biden. He was frustrated that there were not other choices for the top of the presidential ticket, and was convinced that Mr. Biden was not entirely up to the duties of the office.

Still, Mr. Wells plans to cast his ballot to re-elect the president in November.

“He’s incompetent. He’s clearly struggling to fulfill his duties,” he said. “He’s clearly reached the point where he’s too old for the job. But he’s still a step ahead of Trump.”

Camille Baker contributed reporting.

The New York Times/Siena College poll of 980 registered voters nationwide was conducted on cellular and landline telephones, using live interviewers, from Feb. 25 to 28, 2024. The margin of sampling error for the presidential ballot choice question is plus or minus 3.5 percentage points among registered voters. Cross-tabs and methodology are available here.

Claude Folmer was about 40 years old the first time he visited the Mer de Glace, the largest glacier in the French Alps. He remembers enjoying the panoramic view from the observation platform, then taking a short hike down to the ice, where he toured the ice cave that’s carved into the glacier’s surface.

Four decades later, on a mild, sunny morning in early February, Mr. Folmer — now 80 and accompanied by his adult son, Alain — was taking in a view of the same glacier. He was shocked by the change.

“The difference is enormous. The glacier used to be just below,” Mr. Folmer said, gesturing to the gravel-covered river of ice that now lies more than 800 vertical feet below the viewing platform. “For someone who doesn’t know how it used to be, it’s a beautiful scene. But when you know the difference, it really is sad,” he said.

Mr. Folmer, who lives near the French city of Albertville, traveled by train to Chamonix, the mountain town from which visitors can easily visit the glacier. He and his son happened to be there on the opening day of a gondola that transports visitors between the viewing platform and the ice below. The Folmers weren’t aware of the new lift — which replaces an older gondola built in 1988 — but when they learned of the news, neither was pleased.

“At some point, you have to leave the glacier alone,” the younger Mr. Folmer said. “There’s big machinery being installed. Where will it stop?”

It’s a question that many travelers are asking themselves, as climate change threatens a growing number of tourist destinations — from glaciers to coral reefs, ski slopes to low-lying islands. For thousands of years, humans have raced to be the first to scale a peak, cross a frontier, or document a new species or landscape.

Now, in some cases, we’re racing to be the last.

The term last-chance tourism, which has gained traction in the past two decades, describes the impulse to visit threatened places before they disappear. Studies have found that the appeal of the disappearing can be a powerful motivator. But in many cases, the presence of tourists at a fragile site can accelerate the place’s demise.

There is some evidence that a visit to a threatened place can inspire meaningful behavioral change in visitors, potentially helping to offset the negative impacts of a trip. But research is still in its early stages, and results are mixed.

In a place like Chamonix — where tourism is the mainstay of the economy, and where climate change is already having palpable effects on tourist offerings — such tensions are playing out in real time. The shift to a new way of interacting with the landscape may be slow to come, as many jobs — as well as tourist habits — are built into the old way of doing things. But some are already pioneering a new approach, and with the effects of global warming accelerating, change will have to come quickly.

A new gondola in Chamonix

The Mer de Glace, or Sea of Ice, which once reached from the slopes of Mont Blanc all the way to the valley floor in Chamonix, has been attracting visitors for nearly three centuries. Mark Twain, Mary Shelley and Alexandre Dumas were among the early tourists who visited Montenvers, the site of the Mer de Glace overlook, and helped spread the glacier’s fame.

These days, in a typical year, about half a million people visit Montenvers, said Damien Girardier, the head of the site, which is owned by the city of Chamonix and managed by the Compagnie du Mont Blanc. Most visitors arrive via the red cogwheel train that links the viewing platform to the middle of Chamonix, though some arrive on foot — or ski in. Every year, about 80,000 people ski down the Mer de Glace, a classic backcountry Alpine descent called “la Vallée Blanche” (the White Valley) that finishes near the glacier’s terminus below the viewing platform. They then either hike up to Montenvers with their skis — or they take the lift.

The new lift, which opened the first weekend of February, was built about a quarter of a mile up the valley from the 1988 lift, anticipating the glacier’s further retreat. In the 35 years since that old lift was constructed, the glacier has drawn back so much that about 600 steps had to be installed between the bottom of the lift and the surface of the ice. That made it harder for older adults and anyone with reduced mobility to reach the glacier from Montenvers. It also made for a long uphill slog for tired Vallée Blanche skiers at the end of a long day.

Mr. Girardier said the new lift, which cost 20 million euros, or about $21.6 million, was built in accordance with strict environmental controls. Its colors were chosen to blend into the landscape, a special cable was used to minimize noise, and most of the building material was transported to the site by train. The gondola was also constructed in a way that allows future generations to dismantle the structure easily — should they want to.

“In 15 years, the end of the glacier will probably have reached the lift,” Mr. Girardier said, “but it doesn’t matter. When you go to Iceland, people walk for an hour to get to the glacier. For us, it’ll be the same.”

The new lift is part of a bigger project that will also include the construction of a new educational exhibit, called the Glaciorium, about glaciers and climate change. The center is scheduled to open late this year, though some of the funding has yet to be confirmed.

In the meantime, day-trippers can visit the ice cave, which has been revamped with a new design and information displays, while skiers will be able to take the lift to end a day of skiing on the Vallée Blanche, an important source of work for Chamonix’s guiding community.

Julien Ravanello, a mountain guide with the Compagnie des Guides de Chamonix, leads about 20 Vallée Blanche trips per season. He said the new lift would make things more straightforward on a route that — with a guide — is within the grasp of most average skiers.

“Above all, we like it because it shows people the universe of the high mountains,” said Mr. Ravanello, who added that such an accessible glacial ski descent “is almost unique in the world.”

Capucine Pénicaud, a global health consultant and yoga instructor who lives in Chamonix, skis the Vallée Blanche once or twice a year.

“It’s a place that I love and at the same time makes me very sad,” Ms. Pénicaud said of the glacier, adding that her visits to the Mer de Glace almost always move her to tears. “I think there’s a real opportunity in going there, because you can understand global warming — and feel it,” she said.

But Ms. Pénicaud isn’t happy about the new lift. She said she didn’t mind the 45-minute hike up to the viewing platform at the end of a Vallée Blanche run. Also, the concrete for the project was mixed in the Chamonix Valley, near where she lives, then transported by helicopter to the site. “For the past two years, I have seen helicopters bringing concrete up here every half-hour. How much petrol? How much pollution? How much concrete?” she said.

The Compagnie du Mont Blanc confirmed that concrete for the project had been transported by helicopter, but added that the train had been prioritized for the transport of other building materials “for ecological reasons as well as financial ones.”

Last-chance tourism

Can a visit to such a site prompt a change in behavior?

Researchers at the Mer de Glace have found that exposure to its fragile environment can inspire people to adopt environmentally friendly behavior — or at least to declare their intention to do so in a questionnaire.

A 2020 survey of summer visitors to the glacier found that 80 percent said they would “try to learn more about the environment and how to protect it.” Another 82 percent said they would stop visiting glaciers if doing so would protect them, while 77 percent said they would reduce their water and energy consumption.

More research would be required to see whether tourists follow through. But drawing on the survey results, the researchers concluded that using last-chance tourism as an opportunity to educate visitors about climate change — while also engaging people’s emotions and showing them concrete steps they can take to protect the environment — could maximize the environmental benefits of this kind of tourism.

Others are skeptical. Karla Boluk, a professor in the department of recreation and leisure studies at the University of Waterloo, in Ontario, pointed to her research that found that a majority of last-chance tourists at two Canadian sites were unwilling to pay for carbon offsets.

“There’s an ethical paradox of last-chance tourism, and it involves the moral question of whether travelers acknowledge and respond to the harm they promote,” Dr. Boluk said.

“It’s important for us to engage in thoughtful decision-making and careful research to ensure that we are not contributing to the collapse of these places, exacerbating the issues caused by climate change,” she said, adding that tourist “destinations” are also places locals call home.

A different approach

Elsewhere in the Chamonix Valley, the staff of the Research Center for Alpine Ecosystems is working to understand the potential impact of a different approach to nature tourism: citizen science.

Colin Van Reeth, an ecologist and the manager of citizen science programs at the center, described outings that he and his colleagues have organized on which participants are invited to stop at a pond during a hike to document the frogs they see. “For us, it’s a question of getting tourists involved in naturalist observations of the mountains,” Dr. Van Reeth said. Their hypothesis is that by strengthening people’s sense of connection with the natural environment, they might be able to inspire people to make lasting and meaningful changes to their behavior.

“It’s about identifying those small steps, those small stages of transformation,” Dr. Van Reeth said.

Some don’t need a nudge.

Standing at the overlook, Mr. Folmer, the 80-year-old visitor, said that he gave up flying two years ago out of concern for the climate, and that he makes local trips on his bicycle when he can.

“I don’t blame people who fly occasionally when they go on vacation,” Mr. Folmer said, looking down at the glacier. “But when you see this, you think each of us can make a little personal effort.”

Paige McClanahan, a regular contributor to the Travel section, is the author of “The New Tourist: Waking Up to the Power and Perils of Travel,” forthcoming from Scribner on June 18.

Follow New York Times Travel on Instagram and sign up for our weekly Travel Dispatch newsletter to get expert tips on traveling smarter and inspiration for your next vacation. Dreaming up a future getaway or just armchair traveling? Check out our 52 Places to Go in 2024.

The first thing Representative Marie Gluesenkamp Perez told donors gathered at a recent wine-and-cheese campaign fund-raiser was of the role she played in securing $600 million in federal funding to rebuild one of the region’s main arteries, the aging Route I-5 bridge.

“Bringing that grant home was a dogfight,” said Ms. Perez, 35, a first-term Democrat from a rural, working-class district in Washington State that twice voted for former President Donald J. Trump, and who is facing one of the toughest re-election races in the country this year.

“My community is going to build that bridge,” she told the roomful of gray-haired donors gathered in a packed living room in Washougal, Wash., with giant windows overlooking the Columbia River. “This is our work.”

Ms. Perez considers this funding to be a major coup for her district and her re-election campaign. But the bridge in one of the country’s most competitive districts has become a political piñata in the race, which is all but certain to pit Ms. Perez against the far-right Republican Joe Kent, whom she beat in 2022 by less than 1 percentage point.

Mr. Kent, who denies the legitimacy of the 2020 election and has referred to those jailed for taking part in the Jan. 6, 2021, attack on the Capitol as “political prisoners,” has branded the reconstruction plan an “Antifa superhighway.” He has claimed that the proposed project, which includes a light rail and tolls, will bring unwanted urban elements from Portland into the car-centric, predominantly white community of Clark County, Washington, effectively serving as “an expressway for Portland’s crime & homeless into Vancouver,” as he wrote on social media.

It is an example of how Republicans, many of whom opposed President Biden’s sweeping $1 trillion infrastructure law, are seeking to transform even the most basic of local issues into battlegrounds in the nation’s culture wars in elections this year in which control of Congress is at stake. Mr. Kent’s attacks, which rely on buzzwords of the hard right, place the bridge at the center of a national political discussion that vilifies the left and plays on fears of demographic change.

“We don’t want the problems of downtown Portland dumped right into our district in Vancouver,” Mr. Kent said recently in a Facebook Live chat. “If you look at the murder rate, the crime rate, that’s the last thing we want in Vancouver.”

Republicans have long opposed making investments in mass transit, favoring spending on highways instead. Mr. Kent says he wants the historic bridge to be preserved, with more highway lanes built elsewhere to alleviate congestion.

Mr. Kent declined to be interviewed, agreeing to provide comment for this story only in writing. After The New York Times sent his campaign a list of questions, his aides blasted it out in a news release along with responses.

In the release, Mr. Kent denied that he was playing on racist fears in opposing the bridge project and accused Ms. Perez of lying about her role in funding it, even as he blamed her for mishandling it.

“The drug addicts and criminals in their tent colonies that are spreading their crime from Portland into Vancouver are almost entirely white, and Antifa is overwhelmingly white,” Mr. Kent wrote.

While Portland is predominantly white, it has the largest immigrant population in Oregon, and has seen more than 1,400 refugees arriving from Afghanistan since August 2021. As the city has struggled to provide temporary shelter to migrants arriving from the southern border, Mr. Kent has claimed that Democrats are allowing “illegal invaders” to flood into American communities.

Mr. Kent said Ms. Perez’s true priorities were “protecting biological men’s rights to invade women’s sports, spaces and bathrooms” and said her entire involvement in funding the new bridge consisted of “writing a letter to Pete Buttigieg,” the transportation secretary.

In an interview, Mr. Buttigieg said Ms. Perez “absolutely had a role” in the project being chosen to receive the largest grant of its kind.

“We choose projects based on their merits,” Mr. Buttigieg said. “Effective advocates help to illustrate those merits.”

Built in 1917, the Interstate 5 bridge is one of two major crossings between Washington State and Oregon, with about $132 million worth of freight crossing the bridge every day, as well as about 69,000 commuters from Ms. Perez’s district. It is the main connector for an entire region of the Pacific Northwest, but it is widely believed to be at the end of its life.

The span has become so congested that for many hours a day, vehicles crawl across at 35 miles per hour. The entire structure is supported by pilings of Douglas fir sunk in mud — “pretzel sticks in chocolate pudding,” as the mayor of Vancouver, Anne McEnerny-Ogle, likes to describe it — that puts it at high risk of total collapse in the event of a major earthquake.

“There are projects that are just too large and too complex to be done through existing funding mechanisms,” Mr. Buttigieg said, explaining why the project had received such a large grant. “There needs to be extra support.”

He described the Interstate 5 bridge as the “worst trucking bottleneck in the region” and said it was an example of “a bridge designed to the state of the art 100 years ago that can and must be replaced.”

In 2022, Ms. Perez, who ran an auto repair shop, beat Mr. Kent, a Trump-endorsed retired Green Beret whose wife had been killed fighting ISIS, by just two votes in each precinct in the district. Now Mr. Kent is back, hoping to be swept to victory with Mr. Trump at the top of the ticket.

There are other Republicans running in the primary, but Mr. Kent’s emergence from that small field is already considered a fait accompli; the state Republican Party suspended its bylaws so it could endorse him in the primary and outside groups working to keep Republican control of the House are planning to back him.

And Mr. Kent has already turned the Interstate 5 bridge into a flashpoint of his campaign.

“Voters all across the district are rallying behind my message of common sense conservatism: Build a bridge with no tolls and no light rail, get spending and inflation under control,” he said.

As she crisscrossed her district in the rain and snow in her Toyota Tundra last week with her dog Uma Furman in tow, Ms. Perez said she tries not to think too much about Mr. Kent. “I really try not to get in his head that much. I have to not get in D.C.’s head and not get in Joe’s head.”

Ms. Perez tries to stay in the mind-set of her constituents. On Capitol Hill, Ms. Perez is the rare Democrat who often breaks with her party on major votes, often drawing the ire of progressives who she says do not value the priorities of the working class.

“On the floor, I really have to pay attention to my votes,” she said. “It’s this constant analysis of, ‘How much can I afford to piss off people to do what I think is right?’”

Ms. Perez was one of four Democrats who voted for an annual defense policy bill that Republicans loaded full of conservative social policy mandates that would limit abortion access, transgender care and diversity training for military personnel. She defended the vote, saying it was important to support the military and that the Senate was always going to “clean up” the bill by stripping out the partisan amendments she didn’t agree with.

She also sided with Republicans on a bill to repeal Mr. Biden’s student loan relief initiative. And Ms. Perez has supported the censures of two Democrats, Representatives Jamaal Bowman of New York and Rashida Tlaib of Michigan. Still, Mr. Kent has portrayed her as in lock-step with Democrats and Mr. Biden, attacking her for opposing a hard-line immigration bill, among others.

It has left Ms. Perez in a bit of a political no-man’s land. In the capital, her social circle consists mostly of two Republican Bible study groups, one of which includes Representative Richard Hudson of North Carolina, the current chairman of the Republican House campaign arm that is actively targeting her for defeat.

Ms. Perez, along with other Democrats representing districts that Mr. Trump won, “got a pass last cycle; no one laid a glove on them,” Mr. Hudson said at a recent briefing with reporters. He said his job was “educating voters about their records.”

Despite that, Ms. Perez, whose father was an Evangelical pastor, says she often feels more at home among religious Republicans.

“I feel like my party is embarrassed I’m a Christian,” she said. She is broadly dismissive of some of the values of her own colleagues, whom she views as out of touch.

“I hear my colleagues complain about not making enough money,” she said of her fellow lawmakers, who earn $174,000 a year. “You know what the average income in my community is? You should be ashamed of yourselves.” (The average income in her district is $43,266.)

When Ms. Perez was elected, her Republican opponents tried to tag her as someone who would operate as an undercover, West Coast version of Representative Alexandria Ocasio-Cortez, another young, working-class woman whose election to Congress no one had seen coming. But Ms. Perez said she has little in common with the progressive star from New York, nor has she had much to do with any of the other young women in Congress, even socially.

“Our districts are really, really different,” she said of Ms. Ocasio-Cortez. “It is very lonely, working all the time. You go back to your apartment and eat some frozen peas and go to bed.”

At the evening fund-raiser last week, Ms. Perez focused mostly on her work on local issues, but pressed by donors eager to vent their concerns about Mr. Biden and his re-election campaign, she had little praise to offer.

“I’m not here to apologize for his performance or his messaging,” Ms. Perez said. “I have a lot of dissatisfaction with how Biden’s using his power, but when it becomes a choice between that and Trump?”

Later, sitting in her old office in her auto shop before catching a flight back to Washington, Ms. Perez tried not to get too worked up about what would happen if she lost her re-election race. She would return to this more simple life, she said, and be happy not to miss so many bedtimes with her toddler. But the idea of losing to Mr. Kent was hard to swallow.

“It’s just really obnoxious and patronizing when he’s assuming the mantle of fighting for the little guy,” she said. “It might work for one election cycle, but people are going to need jobs. It works until the bridge collapses — and then what?”

The 5-year-old looked nervously at her older brothers, scanning their faces for any sign of distress as needles were swiftly stuck into their upper arms, the syringe plungers pushed in and the measles, mumps and rubella vaccine administered. Whether it was for her benefit or not, they barely flinched.

Then it was her turn. The girl, Oma Nnagbo, looked wide-eyed at the cheerful nurse who a moment later declared, “All done, very brave!”

Michael Nnagbo, 40, had brought his three children to this pop-up vaccine clinic in Wolverhampton in England’s West Midlands after receiving a notice from their school about a measles outbreak in the nearby Birmingham area.

“It’s what we have to do, and it’s important to do,” Mr. Nnagbo said. “I just want them to be safe. And it was easy, you could just walk in.”

Cases of measles, a highly contagious but easily preventable disease, have begun to crop up in clusters as the number of children getting the combined measles, mumps and rubella vaccine has declined globally. The trend worsened after the coronavirus pandemic because of a lack of access and hesitancy among some groups. The measles virus can cause serious illness and, in the most extreme cases, death.

Across Europe, measles cases rose more than 40-fold in 2023 compared with a year earlier — from less than 1,000 to more than 40,000 — according to the World Health Organization. And while much of that increase was concentrated in lower-income nations like Kazakhstan, more prosperous nations, where higher vaccination rates had long made cases measles rare, are also experiencing worrying outbreaks.

In Britain, 650 cases of measles were confirmed between Oct. 1 and the end of February, according to the U.K. Health Security Agency, which declared a national incident in January. The rise in cases was initially driven by an outbreak in the West Midlands, but it has spread elsewhere around the country. Most of the cases in Britain are in children under 10.

Vaccine coverage has waned to precarious rates in some communities, particularly those facing the highest levels of deprivation. That was less the result of a surging anti-vaccine movement, experts said, than a lack of resources, lack of awareness, and some culturally driven hesitancy.

The percentage of children being immunized through the country’s routine vaccination program has fallen over the past decade across all illnesses, including whooping cough, measles, mumps and rubella, polio, meningitis and diphtheria.

England no longer has the levels of vaccine coverage recommended by the World Health Organization, which advises that more than 95 percent of people must have had two doses of a measles vaccine that contains weakened amounts of the virus to prevent outbreaks.

England had 84.5 percent measles vaccine coverage by the end of 2023, but in some areas it was far lower. London had a coverage rate of 73.1 percent overall, even lower than the West Midlands, where the coverage was 83.6 percent at the end of last year.

Jenny Harries, the chief executive of health security agency, said in a statement that the lower vaccine rates were linked to inequality.

“While the majority of the country is protected, there are still high numbers of children in some areas that continue to be unprotected from preventable diseases,” she said. “Unless uptake improves we will start to see the diseases that these vaccines protect against re-emerging and causing more serious illness.”

Carol Dezateux, a professor of pediatric epidemiology at Queen Mary University of London, said the current measles outbreak was “entirely predictable,” as immunizations had fallen to alarmingly low levels even before the pandemic. The causes were complex, she said, but the lockdowns and worries about exposure to the coronavirus made the problem worse.

Vaccination rates for children in England have been steadily declining over the last decade, partly because of vaccine hesitancy but also because of a lack of resources and logistical issues in the most deprived areas. It’s not just the M.M.R. vaccine, Dr. Dezateux said, as there is evidence of widening inequalities between wealthy and poor children across Britain in all five of the key childhood vaccinations.

“There’s a failure to think about how we can move the dial on this,” in a more coordinated way, Dr. Dezateux said, adding, “You might like to climb a high mountain, but if you’ve got no prospect of even getting up to the first base camp, you’re never going to try it, you know?”

The coverage gap has been difficult to close in some areas, Dr. Dezateux said, because so much pressure has fallen onto general practitioners in the country’s National Health Service who are already severely stretched.

Still, the cost of prevention in the form of vaccines is about 4 percent of the cost of an outbreak, she said, showing the need for a cohesive and coordinated plan to work toward better vaccine uptake.

“We know that where resources are brought in, then people can do more. It’s not rocket science,” Dr. Dezateux said.

Dr. Milena Marszalek, a research fellow at Queen Mary who is a general practitioner in northeast London in an area that has one of the country’s worst vaccination rates, said it was a logistical struggle to combat dropping vaccine coverage.

“There is a real problem with lack of capacity, lack of appointments,” she said. “We haven’t got the resources needed to bring the kids in for vaccination.”

Still, some things worked, she said, citing pop-up clinics and outreach with local imams to relay information about the safety of the vaccine to the large Muslim South Asian community in the area.

Local Haredi Jewish families told her that flexible hours at clinics and walk-in appointments also removed a barrier.

Still, it is often only after a significant outbreak that the issue of vaccination takes on greater urgency. Nicole Miles, the lead nurse for Vaccination UK, a group commissioned by Britain’s National Health Service to deliver childhood vaccines and who ran the Wolverhampton clinic, said that an accessible, sensitive and tailored approach was important.

“What people don’t realize is how sick it makes you,” Ms. Miles said of the measles virus. “There is this idea that, ‘Well it’s just measles,’ because we haven’t seen cases of measles for years like we are now. So people don’t realize how dangerous it can be, since it just hasn’t been here.”

Ms. Miles, 34, and two other nurses who were working to distribute the vaccines discussed how vaccine hesitancy among their patients was actually quite rare.

“There are always going to be cohorts of people who don’t want to be vaccinated,” Ms. Miles said. “And essentially, there’s nothing we can do about that, is there? But we need to vaccinate the people who do want to be vaccinated and who have been missed along the line somehow.”

At the Wolverhampton clinic, many of the families coming in said that they were not opposed but had not gotten vaccinations for one reason or another. Like Mr. Nnago, many had heard about the vaccination push through schools.

The Okusanya family, originally from Nigeria, has been living in Wolverhampton for two years. Oluwafunmilayo Okusanya, 42, said none of her three children had received the M.M.R. vaccine in their home country, so when she heard of the measles outbreak locally, she knew it was important to bring them in.

“When the opportunity came, I felt it was a good thing for them to have it,” she said. “It’s made it very convenient. Although some might not see the need to come around for it, we just need to protect the kids.”