Ari Rabin-Havt, a burly, bearded political operative, had been doing events with his boss for three years, since his boss was just 75 years old. But Bernie Sanders had never before asked for a chair. Sanders was as tired as Rabin-Havt had ever seen him, sitting in front of a banner bearing his name at a private fundraiser in a Middle Eastern restaurant in Las Vegas. Rabin-Havt cut the event short. He was a little alarmed, but political campaigns are exhausting, and it had been a long day, beginning early in Eastern Standard Time.

Jesse Cornett, the body man, was with them — his first day on the job. A body man is literally someone who takes care of the needs of the corpus of an important and busy person. It was his job to know how the candidate’s body was faring, but it was not his job to push.

In the car, Rabin-Havt asked if Sanders was okay. Sure, Sanders said. He’d just go to the hotel and lie down. He had a big day tomorrow. Then Rabin-Havt asked about dinner. Sanders said he was not hungry. He hadn’t eaten for hours and hours. Sanders should have been hungry. It could have been nothing, but two alarm bells had just rung for Rabin-Havt, and here came the third: Sanders said he was feeling a tightness in his chest.

Sometimes in high-pressure jobs, at the risk of irritating someone who is paying your salary, you have to substitute your judgment for theirs. Cornett and Rabin-Havt said it at the same time: They should go to an urgent-care clinic. And they did.

Faiz Shakir, Sanders’s campaign manager, got the call around 11:30 p.m. East Coast time. Shakir got the earliest flight out he could and spent his time in the air trying not to come to any conclusions based on information he didn’t have.

The first urgent care they visited, in a strip mall, turned them away, even after learning who the patient was. It was too late, and they were too busy. So Rabin-Havt remembered when he’d stayed at the MGM Grand Hotel and Casino, right on the Las Vegas Strip, that he’d stared out the window at an urgent-care sign. There’s no way around this: The place is called Elite Medical Center.

Sanders went in with the doctors, and Rabin-Havt sat in the waiting room with the senator’s wallet and a pile of paperwork. “There was never a catastrophic moment,” the deputy campaign manager stressed to me in February. The candidate never lost consciousness and never stopped being his irascible self.

Doctors told Rabin-Havt to take Sanders’s glasses away for safekeeping, but with this particular man, that issue proved to be a nonstarter. Eventually, the senator was taken to a nearby hospital. There, he got his artery blockage cleared, and when Rabin-Havt visited he was awake, around 1 in the morning.

Later that morning, “I went into the hospital room,” Shakir told me, “anticipating a tough conversation.” Sanders was sitting up, asking for updates on the campaign, energetic as ever and impatient to get back to work. “I was surprised,” Shakir says. “You know, Are you sure you’re okay? I think he got a little sick and tired of people asking if he was okay.” That is, within 12 hours of his heart attack, Sanders did not want to talk about his heart anymore.

Thus began one of the strangest political arcs in recent memory. Bernie Sanders — a notoriously grumpy Jewish socialist seeking the presidential nomination of a party he does not belong to and often disparages, whose lefty positions include politically tractionless ideas such as allowing convicted felons to vote from their prison cells, whose shlumpy posture emphatically lacks the parallel-to-the-wall bearing of the typical U.S. senator, who sounds like a sufferer of perpetual nasal congestion, who has had a child out of wedlock, who is older today than Ronald Reagan was when he left office already in some state of mental confusion — had a heart attack on Oct. 1. And it was then that his campaign really began to take off. Not only did the heart attack not deter any of his established fans, but more people than ever before began identifying themselves as supporters, and vastly more people opened their wallets.

He surged in the polls; he won the popular vote in Iowa, triumphed in New Hampshire, romped in Nevada. But it turned out there was one last surprise: Just as quickly as Sanders had become the front-runner, he seemed to stall — overrun in South Carolina and on Super Tuesday by a revived Joe Biden, whose own campaign had looked to be finished as recently as a few weeks ago.

How could things go so right and then so wrong in such quick, dramatic succession? Assuming Sanders’s downward trajectory continues, there will be, in the weeks to come, no shortage of autopsies performed on his campaign. Most will focus on the ideological dimension: Was Sanders too far left? Did Democratic voters turn out to be in a more centrist mood than we all thought? Those factors undoubtedly explain a lot, but to those explanations I want to add another theory of both his rapid rise and his sudden demise. It has to do with what Americans want — and don’t want — from their politicians. And Sanders’s heart attack turns out to be the perfect place to start.

Sen. Bernie Sanders (I-Vt.) and his wife, Jane, visit the Iowa State Fair in Des Moines in August. (Salwan Georges/The Washington Post)

Supporters at a rally in January in Sioux City. (Salwan Georges/The Washington Post)

Before everything seemed to collapse for Sanders, I spent a lot of time trying to figure out what, back then, seemed like the central mystery of his campaign: In strictly political terms, why didn’t a heart attack kill him?

History, after all, is replete with examples of ill health seeming to damage presidential campaigns. Bob Dole, 73 and wounded in war, put his weight on an unsecured railing at a campaign event and fell off a stage, with indelible video of him lying on the ground and then getting helped up. Thomas Eagleton, after attaining the 1972 Democratic vice presidential nomination, confirmed news stories that he’d received electroshock therapy for depression, prompting George McGovern to ask him to leave the ticket. Hillary Clinton fainted, or didn’t faint, at a 9/11 memorial event in 2016, giving the Internet a chance to speculate about her health and fitness for office.

Politicians have always acted as if health mattered politically — and as if ill health was therefore something worth hiding. Richard Shenkman, a historian and the author of “Presidential Ambition: How the Presidents Gained Power, Kept Power, and Got Things Done,” notes that once in office a president’s health becomes entwined with public confidence, which in practice means the public gets protected from knowing how perilous the situation might be. During Franklin D. Roosevelt’s fourth presidential campaign, to hide the extent to which polio had ravaged his body and to prove how robust he was, he rode in an open-car parade in the rain for hours, and risked getting much sicker. John F. Kennedy was devastatingly ill with Addison’s disease and was at times pumped full of painkillers and amphetamines to project youth and vigor. President Trump took an unplanned trip to Walter Reed National Military Medical Center in November, but all the public knows is that the president tweeted his health was “very good (great!).”

Given this history, why had the heart attack not hurt Sanders politically? One possibility was that, after Trump, we simply don’t have dealbreakers in American politics anymore. It can be hard to remember as far back as 2015, but a lot of things used to disqualify someone from the presidency. For example, it used to be a big deal if a presidential candidate used a position of authority to burst into teenage beauty contestants’ dressing rooms when they thought they would have privacy. Or if he suggested committing war crimes to a frenzied, cheering crowd. Or if he declared bankruptcy to avoid paying money he had agreed to pay.

Not only has Trump personally obliterated many perceived obstacles to the presidency, he has lowered the bar in another way: If, as many Democrats said from the beginning, what was most important was to support the candidate most likely to beat Trump, then maybe everything else about the candidate had simply become less relevant. Did their policies make sense? Were they competent? Were they healthy enough to be president? It now seemed like Democrats cared only about what candidates did between the time they got in the race and November, not what the candidate might do starting in January 2021.

There was another possibility, too: Promising a revolution — as Sanders has done from the beginning — meant the details didn’t have to be crystallized. Even successful revolutions start in poetry but end in prose. The Founding Fathers declared independence and that all men are created equal in 1776, but it was 13 years and a war until anybody figured out how the government was going to work, and we’re still working on the equality part. So if a candidate said he was going to end gerrymandering and that worked for you, maybe you were going to just believe him when he said his heart was fine. Some people call this magical thinking. Others might call it hope.

Sanders reached out and took the mic before Ryan was ﬁnished. Ryan’s righteous intensity was a gift that Sanders didn’t seem to know how to accept.

Sanders photographed through the red recording light of a TV camera. (Salwan Georges/The Washington Post)

It wasn’t merely, however, that Sanders’s campaign had survived his heart attack. It had actually seemed to do better in the weeks afterward. Shakir told me that over the 24 hours after the heart attack, before there was much reported at all about what happened or how the senator was doing, “We had a huge surge in volunteers making phone calls, volunteer donations to the campaign, surrogates going out and doing events for him. He was so excited to hear that the ‘Not me. Us.’ campaign was coming to fruition.” And when Rep. Alexandria Ocasio-Cortez endorsed him, which Sanders learned would happen while he was still in the hospital, she made it impossible to count him out.

His visible physical resilience and determination were, it seems, changing minds. George Sanders (no relation) — a 45-year-old organizer for the campaign whom I met in January at a Pennsylvania event called Organize Your Friends for Bernie — told me the heart attack was “a wake-up call” that Sanders might not be around forever. “We want change. We don’t want to miss it. Sometimes you need a catalyst. He’s the person to do that. Even if something happens to him, now’s the time to try this. It’s not just him, but he’s the best chance we might have for a while.”

But the theory that I found most intriguing was offered by Shenkman, the presidential historian. I’d asked him to explain how a negative health event might have helped a presidential campaign. “I was baffled by it myself,” he said. “It’s not exactly parallel to Reagan surviving an assassination. You didn’t see him in that heroic mode.” I pushed him to speculate. “People were fascinated by [the heart attack],” he said. “The fact that he suffered from it makes him into a human being. It really helps Bernie’s case because he readily confesses he’s not one of these backslapping politicians. It’s not his brand. He’s a little like a stick-figure cartoon, but a heart attack made him seem human.”

Shenkman was describing perhaps the core feature of Sanders’s campaign. Sanders adores talking about sweeping ideas — and has always seemed to loathe talking personally about himself. But if Shenkman was right, the candidate had, post-heart-attack, taken what would traditionally have been a weakness (lack of apparent interpersonal connection) and another weakness (a heart problem) and forged them into a strength. Because who has heart attacks? Not cartoon figures. Not ideologies. Human beings.

Indeed, there had been a vague idea that after the heart attack Sanders’s campaigning was kinder and gentler, that he was looser and more spontaneous and more able to connect with voters in a personal sense. “His return to the campaign trail,” observed reporter Ruby Cramer in a December BuzzFeed article, “ever since the heart attack, aka ‘heart incident,’ as senior aides refer to it in the press, has been a happy, bordering-on-joyous affair.” Maybe what voters wanted from Sanders, after all this time, was to be more personable, more relatable — more like a normal politician.

Supporters at the St. James complex in Springfield, Va., in February. (Salwan Georges/The Washington Post)

Sanders watches Super Tuesday results backstage at a rally in Essex Junction, Vt. (Salwan Georges/The Washington Post)

But how much of a change had Sanders really made? To what extent had he — the ultimate candidate of grand ideas, of revolution, of structural explanations for society’s problems — acquired a new human touch?

Consider what I witnessed in Grundy Center, Iowa, population 2,700, on a late afternoon in January. Approaching the small community center, I could hear Sanders speaking; the doors were open to accommodate an overflow crowd. Inside, the candidate was onstage. About 200 people sat in front of him, with 20 or so selected to sit behind him and hold signs.

Sanders addressed a war with Iran that looked possibly imminent. He thought war should be a last resort, and that sentiment got applause. He was a little red-faced and paced back and forth. He was in a nice blue sweater and dress pants, both impressively non-wrinkled considering his widely caricatured persona and his recent life on the road. He would wear the identical outfit for the next three days. Did he have several of them? Did he wield an iron late at night, in his hotel room? It’s part of the Bernie mystique.

In person, his hand gestures seemed exaggerated, his long arms pushing his long hands sideways, the palms out, fingers slightly curled, the whole hand flopping as though he were a marionette. The grandiloquent movements seemed a little retro — more befitting a Herbert Hoover-era stump speech shouted from the back of a railroad car, without microphones.

Sanders segued into his favorite topic, health care. He was explaining how he plans to pay for Medicare-for-all, and he was doing it using crowdsourcing. “How much are you paying a month in premiums?” he asked the room. An audience member answered.

“All right. Nine hundred bucks. For yourself? For your family? Two of you. All right. Nine hundred bucks iiiiiis” — he was doing ciphers in his head, kind of like a parlor trick; this is a man from before calculators — “almost $11,000 a year. Do you have any deductibles? Out-of-pocket expenses? Prescription drug costs?” He got the answers, did the math, coughed out the guy’s yearly health expenditures. He’s really into deductibles. His point was that under Medicare-for-all, you pay more taxes, but they are less than your current privately paid deductibles and premiums together. You’re banking more of your money because Uncle Sam has no profit motive to fleece you, the way for-profit companies do under the current unfair, unsustainable system.

A wiry, intense-looking middle-aged man stood up. His name was Ryan. He wore a tan newsboy hat and a plaid shirt with elbow patches over a Bernie T-shirt. Sanders had asked the audience for insurance premium payments, but Ryan ignored that. He started telling a story. “I just went to the emergency room this last Sunday feeling like I was gonna have a heart attack,” he said. Ryan is uninsured, with lingering student debt for both himself and his wife. He didn’t want to leave her with medical bills if he was going to die anyway, “so I begged and pleaded with the emergency room. I let them do the EKG thing” — he tapped his chest. Bernie nodded, flattened his lips, looked down. “I let them X-ray my lungs to make sure it wasn’t pneumonia,” Ryan said, “but then I told them I would walk out.” He felt he couldn’t afford any more tests.

As the tale was spooling out, Sanders looked at the man only intermittently, and only for seconds at a time. Mostly, he shot his glance around the room. He juggles numbers nimbly but isn’t, it seemed clear, quite sure what to do with emotions. It was perhaps the moment for a hug, but Bernie couldn’t quite go there. He extended his long arm to Ryan’s shoulder and simultaneously shook his hand, without getting any closer. Literally, this became an arm’s-length transaction.

Now Ryan was really twisting himself into a knot, comparing his experience at the hospital to his experiences as a poor kid in grade school, with a lunch card of a different color from everyone else’s. The rich kids, he said, made fun of him. He addressed the candidate with almost jarring intimacy.

When he told the hospital he had limited resources, he said, “they referred me to a free clinic. ... It’s humiliating, honestly, Bern. When coming home — I was driving a half an hour so that I didn’t have to have an ambulance — I called my wife, and I said, ‘You f---ing tell Bernie your husband died because he couldn’t afford to get fixed, because they don’t care if the poor drop, they don’t care. They don’t care.’ ”

Sanders was leaning away, his hands behind his back. He reached out and took the mic before Ryan was finished. “And we need you!” Ryan called after it, his big finale line lost to most of the room. Ryan’s righteous intensity was a gift that Sanders didn’t seem to know how to accept.

Candidates need these moments of empathy, to seem human. They tell stories about their struggles, their kids who make fun of them, their spouses who are smarter than they are. Biden’s family tragedies. Mayor Pete’s coming out to his parents. Elizabeth Warren’s being fired from her teaching job upon becoming pregnant.

This particular moment in Iowa was a moment for personal connection. It was a fine moment, in a presidential campaign, to mention that Sanders’s daughter-in-law died just weeks before at 46 from a cancer no one caught until it was too late to treat. That months ago, Sanders was making the same calculus that Ryan did about a possible heart attack. And that the candidate understands this sort of thing. And the candidate does understand. You cannot run this sort of empathy-based campaign and not understand. He just has a hard time showing it.

“Further discussion on premiums?” he asked the room. Someone piped up. It was a woman in the front row, her voice breaking and full of tears. She was not well enough to stand. She and her husband pay a thousand dollars a month, their deductible is $7,000, and he hadn’t had a raise in 20 years. “We can’t do this for much longer,” she said, faintly, tremulously, and through what sounded like physical pain.

“Did everybody hear the woman?” Sanders said. “I’m hearing $1,000 a month, that’s $12,000 a year, plus a $7,000 deductible. ...”

This didn’t seem to me like a looser and more personal campaign. But Faiz Shakir, when I pressed him for examples of Sanders’s new style of campaigning, told me the deductible game was new, since the heart attack. “He starts talking about the insanity of what the deductible is. He would say something like, if you feel like you have to pay $5,000 out of your pocket to go to the doctor, for many people, they are going to choose not to go to a doctor. And that maybe they get sicker.” What had looked to me like a candidate avoiding all signs of empathy was, the way Shakir saw it, actually the kinder, gentler campaigner. But the result wasn’t a personal connection to Ryan. Sanders still wanted numbers, not feelings.

Sanders’s blue eyes were hard and chiding. I got the impression that if I uttered one more word, he was going to call my dad.

A supporter carries a portrait of the candidate at the Super Tuesday rally in Vermont. (Salwan Georges/The Washington Post)

In December the New York Times editorial board asked Sanders, “What are you likely to fail at or to do poorly as president?” Not the conventional “What is your biggest weakness?” but the much more interesting “What will be your obstacle?” He was both clear-eyed and unapologetic.

He’d fail, he said, to “talk to the New York Times.” And what he said next might have been to the same point, or it might have been a new one. “Look, I don’t tolerate bulls--- terribly well, and I come from a different background than a lot of other people who run the country. I’m not good at backslapping. I’m not good at pleasantries. If you have your birthday, I’m not going to call you up to congratulate you so you’ll love me and you’ll write nice things about me. That’s not what I do. Never have.”

What journalists want is a story: who you are and what made you this way. How you went from A to C. Instead, as Sanders explained, “I try to stay focused on the important issues facing working families in this country, and I fight for them.” Exactly what he did with Ryan, in other words. He stayed focused on what’s important — to him.

In the same interview with the Times, Sanders gave us an example of himself not tolerating the b-word:

NYT: Can you give us an example of one person who’s broken your heart?

BS: [after a long pause] What, on a personal level?

NYT: Yeah.

BS: No. I won’t. Even candidates for president of the United States have a limited amount of privacy.

If Super Tuesday was the end of Sanders’s shot at the presidency, he might have put his finger on why. The backslapping dealmaker Joe Biden, whom people like to work with, got the endorsements and the infrastructure of a whole political party of people who understand the value of remembering birthdays. Biden is in many ways the opposite of Sanders: a man who doesn’t do very well at all with big ideas but excels at the human aspect of politics. And it may simply be that for most voters, or at least many voters, the human aspect is the core of politics — especially in a time of crisis and fear.

I had tried to get an interview with Sanders through the campaign, or be granted the opportunity to shadow him. No luck. And yet, after Sanders’s Iowa swing was over and everyone was heading home, I wound up getting both, in a weird way. On the flight out of Iowa to a connecting flight in Chicago, I sat only a few feet behind him.

True to character, Sanders had carried his own luggage onto the plane and kept his head down at check-in. Unassumingly, he had boarded after the military. No body man in sight.

For both of us, the political opportunity here was actually better than a sit-down interview. It was potentially more authentic. Reporter and subject would be trapped together, breathing the same air at 30,000 feet. It wouldn’t even take any time out of his schedule. People want to know what the man is like. And anything he did and said in this familiar circumstance would instantly be more likable, more human, more believable than a Q&A or a debate. This would be his low-stakes chance to demonstrate some graciousness in a familiarly awkward situation. To show he’s the candidate you want to be stuck with on an airplane.

As soon as the fasten-seat-belts sign went off, I was crouching in the aisle with my notebook. “No,” he preempted, after the introduction but before the first question. “No. I am not doing press interviews now. I am sitting here reading” — he gestured to his tablet. It seemed to have text and a bar graph on it. “I am going home.”

One question, Senator? “No. Who are you?” he asked. “No. It’s inappropriate.” His blue eyes were hard and chiding. I got the impression that if I uttered one more word, he was going to call my dad. I slunk back to my seat, chastened, mystified.

But now maybe I get it. Just like with Ryan in Grundy Center, and just like with the New York Times editorial board, just like with every opportunity to show us his humanity, Bernie Sanders kept himself to himself. From his perspective, we already knew too much about his heart.

Rachel Manteuffel is a Washington Post editorial aide.

Photo editing by Dudley M. Brooks. Design by Christian Font.