When Democratic presidential candidate Bernie Sanders suffered a heart attack in October, what upset his long-time supporter Craig Althof the most was the way it was covered by the media.

In the opinion of 65-year-old Althof, who had a similar procedure to Sanders to prop open an artery, journalists were too quick to write Sanders’ political obituary, speculating that the 78-year-old’s second White House run was likely over.

“I’m a two-stent guy, just like Bernie,” said the substitute teacher in Newton, Iowa. “It opened people’s eyes that they’re out to get him.”

Four months later, the progressive firebrand’s turnaround — a virtual tie for first place with Pete Buttigieg in last week’s Iowa caucuses and another strong showing likely in New Hampshire on Tuesday – is at least partly thanks to the passion of supporters like Althof, who says the way the U.S. Senator was written off reminds him of the 2016 nominating race – which Sanders ultimately lost to Hillary Clinton – all over again.

Those fans were determined that the outcome would be different this time.

In the week following the heart attack, staff and volunteers held nearly 300 events in Iowa alone, from house parties to canvassing outings, and made 800,000 calls in four days to early voting states including Iowa and New Hampshire, campaign officials told Reuters at the time.

Days later, Sanders won the most sought-after progressive endorsement from first-term Congresswoman Alexandria Ocasio-Cortez, the first of a string of endorsements.

More than any of the other 10 Democrats vying for the right to take on Republican President Donald Trump in November, Sanders leans heavily on this fervent core of supporters for donations and for canvassing voters, an approach summed up by his slogan “Not me, us.”

Sipping a beer at Sanders’ post-caucus party in Des Moines last week, Michael Tunney, 34, said he traveled from Los Angeles to knock doors for Sanders, and was planning to do the same in Nevada ahead of the caucuses there.

“It’s easy to do because you don’t feel like you’re selling something,” he said. “When you knock on doors you have nothing to be ashamed of, it’s not like your a used car salesman, because you know you’re right on all the issues.”

Sanders raised $96 million in 2019, more than any other Democratic contender. In January alone, Sanders raised $25 million, according to the campaign, some of which would be put into the 14 states that vote on March 3, known as Super Tuesday.

These are all strong signs Sanders may be building a progressive version of the populist wave that swept Trump into office in 2016, observers say.

But the analogy to Trump is exactly what makes many skeptics uncomfortable.

Sanders’ fiercest supporters can be unwilling to countenance criticism of their candidate and seem ready to back him almost no matter what he does.

Sanders himself has shown no interest in reaching out to the Democratic Party’s moderate wing, which rivals believe would become a major liability if he became its nominee.

Instead, the self-described Democratic Socialist has continued to push the message in recent weeks that he is taking on establishment Democrats.

“We are their worst nightmare,” he said in a Sioux City rally on Jan. 26, referring to the party hierarchy as well as Trump and business interests that he said were “nervous” at the idea of him in the White House.

‘STAUNCH ON HIS VALUES’

That unapologetic stance may have helped him with many liberals who had been weighing him versus fellow liberal U.S. Senator Elizabeth Warren, who was building momentum with a similar policy platform before Sanders’ heart attack. Both support Medicare for All – a single, government payer system that would all but eliminate private healthcare.

Warren’s separate proposals since then – that she would finance Medicare for All without any tax increases on the middle class, and that she would seek a gradual transition into the system – have sparked criticism from all sides.

Moderates accused her of lying to taxpayers. And more than a dozen Sanders supporters who had been considering Warren told Reuters in recent weeks they saw the idea of a transition as a sign she was moving to the center.

Sanders won 26.1% of state-delegate equivalents in Iowa’s first-in-the-nation caucuses, just behind Buttigieg’s 26.2% but well ahead of Warren, who finished third with 18%, and former vice president Joe Biden, who had 15.8%.

“I feel like Warren is becoming less progressive to kind of cater to Republicans. That’s what Hillary did in 2016 and it obviously didn’t work,” said Marisa Rude, 19, a freshman at the University of Iowa, who switched from Warren to Sanders in the past month and was volunteering for his campaign in January.

“So that’s why I’m for Bernie. I think he’s staunch on his values.”

TWO DOORS A SECOND

Sanders held on to some key staff in Iowa from his 2016 campaign and had built up a formidable organization by October, with 112 staff working out of 16 offices.

His campaign spent nearly $6 million to air television ads 20,272 times in Iowa, according to data published last week by Wesleyan Media Project. Only billionaire Tom Steyer and Buttigieg outspent Sanders on TV in the state.

In Iowa, the campaign said it knocked on 500,000 doors in January. At one point staffers and volunteers knocked on two doors every second over a five-hour period, said Misty Rebik, Sanders’ Iowa state director.

In the days before the caucuses, Sanders’ campaign was looking strong – enough to prompt moderates to try to stop his surge, airing television ads arguing that a socialist cannot win in many of the states beyond Iowa.

Supporters like Rod Sanders, 53, dismissed those concerns.

“I’d rather have the guy over here who’s trying to get me the best deal possible, instead of conceding from the start,” he said. “And maybe America needs scaring a little bit.”

(Reporting by Simon Lewis; Editing by Soyoung Kim and Sonya Hepinstall)