About three weeks ago, Vermont Sen. Bernie Sanders had a heart attack that threw his campaign into question. But now, it's more apparent than perhaps at any point in this presidential campaign that the 78-year-old white-haired politician and his revolution will remain a powerful force in the Democratic primary.

Sanders' campaign has a renewed vitality following a record-setting rally in New York over the weekend, a strong debate performance last week in Ohio, an infusion of campaign cash that translates to having more money on hand than any other Democratic presidential candidate, and endorsements from two of the most progressive women of color in Congress: Minnesota Rep. Ilhan Omar and New York Rep. Alexandria Ocasio-Cortez.

His campaign is optimistic and emboldened with a clear mission: prove the senator's skeptics wrong and quash any lingering questions about his health and ability to serve after his heart attack.

"In the professional pundit class, in the elite media circles, there's been a strong effort to discount Bernie Sanders: 'The movement is over, he can't succeed. He doesn't have opportunities for him to grow, it's gonna end for him,'" said Faiz Shakir, Sanders' campaign manager, paraphrasing what he sees as a problematic narrative.

But Shakir contends that the last week proves the pundits wrong.

"Sanders has shown that he has the support and the stamina to stick around," he said.

On Saturday, the white septuagenarian was joined by perhaps the most well-known Latina in politics, the 30-year-old Ocasio-Cortez — an alliance that countered the "Bernie bro" caricature of his 2016 campaign. Ocasio-Cortez, a darling of the progressive left, officially offered her stamp of approval to the Vermont senator.

"For me, the mass movement, mobilization and the decades of work that have gone into that was a personal tipping point," Ocasio-Cortez told NPR's Michel Martin on Weekend All Things Considered, explaining why she specifically supported Sanders over a progressive woman in the field (such as Massachusetts Sen. Elizabeth Warren). "It's far larger than a presidential campaign, this is about really creating a mass movement ... to guarantee health care, housing and education."

Sanders and Ocasio-Cortez were met in Queens, N.Y., by a crowd that campaign officials estimated exceeded 25,000 people — a rally larger than any other Democratic candidate has seen this campaign.

'A loyal, strong base'

Sanders is not the first presidential candidate in history to have had a heart attack. In fact, Dwight D. Eisenhower suffered from one in 1955, a year before he was re-elected for a second term.

But Sanders has long been scrutinized for his age, and the moderators on the debate stage in Ohio last week were eager to get a response from him on record.

"I'm healthy, I'm feeling great," Sanders quipped at one point, "but I would like to respond to that question," he added, as he jumped into a conversation about the opioid epidemic and drug companies.

Analysts and experts agreed Sanders looked and sounded healthy on stage.

His positive debate reviews came on the heels of new fundraising numbers that showed his campaign had $33.7 million on hand at the end of the third fundraising quarter — more cash than any of his Democratic opponents, and notably more than three times as much money as former Vice President Joe Biden.

"If history is any guide, don't count Sen. Sanders out, he is someone who I think will be with us in this campaign for quite a while," said Karen Finney, a Democratic strategist who worked for Hillary Clinton in 2016. "We know that he's got a loyal, strong base of support."

Mark Longabaugh, a Democratic consultant who worked on Sanders' campaign in 2016, pointed out that part of the senator's fundraising advantage was his 2016 campaign operation.

"Just in a technical sense he came into this race with by far the largest fundraising list of any of the candidates," said Longabaugh. " And that was underestimated by a lot of people."

For Finney and Longabaugh, the main question is how and if Sanders can regain his standing in the polls.

Even before his heart attack, Sanders' poll numbers had begun dropping. And the conventional wisdom was that the Democratic primary was winnowing down to a two-person contest between Biden and Warren.

Shakir is dismissive of the polls and insists they don't capture Sanders full support, but he also acknowledges that the senator has a steep path to the nomination.

"The path for Bernie Sanders to win this nomination is arguably the hardest and most ambitious path of any candidate," he said.


Because Sanders base of support comes from young and lower-income Americans - people who usually vote at far lower rates than older and wealthier voters.

"He is trying desperately hard to increase voter participation," said Shakir.

An urgency to differentiate

Strategists say it's not enough to have a strong debate performance or bring in lots of money from devoted supporters, Sanders, they say, also has to figure out how to blunt Warren's momentum.

One possible option is to focus on progressive policy.

Sanders has been trying to prove that he's the furthest left candidate in the field.

For some of his supporters, that strategy is particularly effective on health care. Sanders, as he likes to point out, wrote the "damn bill" outlining a Medicare for All system. Warren has endorsed his plan, but, thus far, she has not laid out how she would pay for it.

"The Medicare for All message has sort of been his bread and butter, and I think that is still a powerful issue at the grassroots," said Longabuagh.

Longabaugh, who is not working for Sanders this cycle, says part of the Vermont senator's resiliency goes back to his consistency, particularly on healthcare.

Shakir says his loyal support is also about trust.

"You just trust that this is somebody who has a lifetime of consistency and that when he gets into the oval office, and he says he's gonna fight for Medicare for All, he's gonna fight for Medicare for All," Shakir said. The indirect assumption from Shakir's statement is that Warren, the other leading progressive candidate in the field supporting Medicare for All, cannot be trusted as much as Sanders to keep their word on the issue.

Sanders has also attempted to outflank Warren on one of her signature campaign issues: a wealth tax.

He recently proposed a plan that goes even further than Warren's and, as our colleagues at Planet Money pointed out, it "could have one large unintended consequence: It makes Warren's wealth tax look moderate."

Sanders has been hesitant to go after Warren directly. The two senators are friends and allies in the Senate, but strategists say there is an urgency for Sanders to differentiate himself soon. Time is running out before the all-important early states start voting.

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