In an era in which conventional political wisdom has been set ablaze, Sanders has challenged the notion that a major health issue is an automatic death knell for a presidential candidate. His age and health remain serious long-term question marks — at 79 in Jan. 2021, he would be the oldest person ever inaugurated into office, a fact that could well draw more scrutiny as voting approaches.

But so far, at least, Sanders has weathered his heart attack and then some.

“Sanders’ standing has only increased since he had that incident,” said Jeff Link, a longtime Iowa Democratic strategist. “It was a wake-up call for people who were totally committed to Bernie, like: ‘We got to make this time count."

Three events last week in the first-in-the-nation caucus state illustrated his comeback: With Ocasio-Cortez campaigning alongside alongside him, his campaign pulled in larger crowds at each stop than it had at any others in Iowa this year. His first rally after his heart attack, which was held in New York City with Ocasio-Cortez, likewise attracted about 26,000 people, according to his team, which would make it the biggest event of any Democratic presidential candidate this year.

Sanders is still third in national polling averages and faces a primary electorate that has expressed concerns about older candidates generally and him in particular. A Huffington Post/YouGov survey conducted a week after his heart attack found that 42 percent of Democrats said Sanders’ physical condition was not good enough to serve as president.

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But Sanders' health scare has not spelled the end of his campaign as some pundits thought it might. Since his campaign announced on Oct. 2 that he was hospitalized, he has gone up about 3 percentage points in Iowa surveys and 2 points in New Hampshire, according to Real Clear Politics’ averages. His national polling has held steady.

Sanders’ aides argue his polling and large rallies are the result of a long-planned strategy: They say they always expected for the young and working-class voters he appeals to most, including some of Joe Biden’s supporters they think he can win over, to tune into the race around this time of the year.

But they also think his hospitalization paradoxically helped him consolidate his base. Reps. Ilhan Omar and Ocasio-Cortez both told Sanders they were backing him soon after his heart attack. Before his health scare, Sanders had been eclipised by Elizabeth Waren in national polling and fell to the low double digits in some early-state surveys.

“AOC referred to it as a gut-check moment for her,” said Faiz Shakir, Sanders’ campaign manager. “I wouldn’t dispute the notion that it caused some people to envision a race without him.”

Ocasio-Cortez’s endorsement, in turn, appears to have influenced some Democratic officials: “I’d be remiss if I didn’t say it was inspiring to see someone like AOC and Ilhan Omar and others stand up to be counted,” said Linn County Board of Supervisors chairman Stacey Walker, who is now Sanders’ Iowa campaign co-chair after announcing his support in late October. “Yes, it weighs on me and it influences me.”

Camron Johnson, an 18-year-old college student who attended a recent Sanders rally in Iowa, said his health didn’t concern him: “It’s probably better than what Trump has going on.”

Scott Punteney, leader of the Pottawattamie County Democratic Party, said that Sanders’ heart attack was initially troubling to some Iowa voters. “But I think people got over it pretty quick because they realized how far medicine has come in 20 years and how people recover from that," he said.

Sanders’ style of campaigning has also changed slightly in recent weeks. He is telling more jokes on the stump and emphasizing a message of solidarity. At an event in Iowa last week, he said, “We become more human when my family cares about your family and your family cares about my family.”

He published an essay on Monday titled “How to Fight Anti-Semitism,” which explored his Jewish heritage and family’s immigrant roots, something his aides have urged him to talk about more.

“Maybe it’s just that he’s feeling better. Maybe it’s nothing more than that,” said Jeff Weaver, a senior adviser to Sanders who has known him for decades. “He is far more energetic now than he was in the summer.”

Sanders, the oldest candidate in the presidential race, had two stents inserted to address a blockage in his artery. Doctors say the procedure leaves many patients feeling more lively.

In recent weeks, Sanders’ campaign has begun airing TV ads in the early states, which could be a factor in his slight uptick in polls there. Sanders has also contrasted himself somewhat with Warren, who has cut into his base of young and liberal voters. In the last month, Warren has fallen in national polling averages.

Sanders’ field team has also recently started the work of trying to persuade potential voters over the phone and in person, his aides said. They previously were contacting people largely to identify their level of support or opposition.

Whether Sanders will stick to the strategy of being more personal and lighthearted on the campaign trail is an open question. After making his life story a centerpiece of his 2020 kickoff events, he didn’t talk about it much on the stump for several months.

He also faces the enormous challenge of still needing to either expand his base or grow the electorate in order to beat expectations and win the primary. If he made it to the general election, Republicans would almost certainly seize on his heart attack the way they seized on Hillary Clinton’s bout of pneumonia in 2016.

But some political insiders said it would be unwise to discount him, especially after his unlikely comeback.

“That whole campaign has been run better than the 2016 operation,” said Link. “They’ve been doing a bunch of innovative things, and people who kind of look past them will make a mistake.”