Mr. Sanders has rebounded thanks to a supporter base more devoted than any other candidate’s, their loyalty stoked by his consistent messages on health care and climate change plus, for some, an unwavering sense he was denied his shot in 2016 by the Democratic establishment.
He has capitalized on the moment to expand his base and turn it into a small-donor army, which raised $96 million in 2019, including $1.8 million that comes in monthly from 200,000 people who have signed up to make recurring donations. The campaign had 300,000 new donors in the last quarter as part of a $34.5 million haul. Better yet, it says, 99.9% of his donors haven’t hit the federal contribution limit, meaning they might be tapped for more.
This success has come while Sen. Warren, his leading rival for the most liberal voters, has taken heat from other candidates over details of her health-care proposal and faded in the polls. Mr. Sanders has largely avoided such scrutiny, for now, allowing him to build support as she has sagged in national and early-state polling.
Sean Lewis, a nonprofit consultant who is vice chair of the Democratic organization for Salem, N.H., told the Warren campaign this past summer he was backing Ms. Warren. But after what he called a few weeks of soul-searching, Mr. Lewis, 37, said he came to the conclusion “I should be backing the candidate who is pushing for wholesale change, and…has been pushing for that kind of change since even the earliest days of his political career.”
With less than a month until the Iowa caucuses that kick off the nomination season, Mr. Sanders’s team is emphasizing his long-term support for a Medicare-for-All system by centering campaign events on individual voters’ health-care stories.
The team is urging its many young supporters to reach out to their friends and parents, and it’s banking on winning votes from groups that often don’t vote in high numbers, such as young people and minorities.
The campaign also is counting on the Democratic field remaining fractured, which would mean that none of his more moderate rivals, such as former Vice President Biden or former South Bend, Ind., Mayor Pete Buttigieg, consolidates support. Unlike Mr. Biden, Mr. Sanders has never polled above 30% among Democrats nationally in this election cycle, though he has consistently been in the top tier.
The leaders in Iowa and New Hampshire are separated by only a few percentage points—margins that could change quickly. Though letters from doctors released recently said the 78-year-old Mr. Sanders was healthy and able to take on the duties of the presidency, he still faces questions about his age and health, largely from older voters, many of whom have never warmed to his candidacy.
He also faces the continuing worry from critics that as the nominee, Mr. Sanders, a self-described democratic socialist, might turn off independent or Republican voters who otherwise could be persuaded to vote Democrat.
“I hope that the Democratic Party nominates a moderate,” said Bill Engler, a 79-year-old retiree from Anthem, Ariz. “I’m a realist, so I want the Democratic Party to nominate someone that can’t just [win] a primary but win the general election.”
The Sanders campaign points to polling that shows the senator beating President Trump in battleground states as an example of his electability.
Mr. Sanders’s heart attack came at a time, the first of October, when he was struggling to gain momentum against Ms. Warren and Mr. Biden.
Following news of the heart attack, “I guess I was a little bit worried,” said Katelin Penner, a student at Wesleyan University in Connecticut.
“But not really,” she added, because as soon as she saw that Mr. Sanders was using his health problem as a chance to push for Medicare-for-All, she figured he would be fine.
Mr. Sanders soon gave his supporters something to celebrate when, during his recovery, three influential progressive lawmakers decided to endorse him. When he returned to the trail in mid-October with Rep. Alexandria Ocasio-Cortez, he drew the largest crowd of his campaign. Framed by the Queensboro Bridge in New York City, he announced he was “more than ready to assume the office of president of the United States.”
Shortly after his return to campaigning came Ms. Warren’s dip in polling. Early on, the Massachusetts senator had said she was “with Bernie” in his call to eliminate private health insurance and replace it with a government-run program.
Mr. Sanders has said he would introduce legislation to do that in his first week in office. He hasn’t specified how he would pay for it, just saying taxes would go up—and not excepting middle-class taxes. Mr. Sanders also says there would be no premiums or co-pays, so the overall cost of health care would go down.
Ms. Warren, by contrast, has said she would pay for Medicare-for-All without raising middle-class taxes. In addition, she said that instead of starting it right away she would transition to it. First there would be an interim plan—looking similar to Mr. Biden’s and Mr. Buttigieg’s proposals—before she would push a Medicare-for-All bill during her third year in office.
That stance has dogged the Massachusetts senator on the campaign trail. At an event in Manchester, Iowa, a woman told Ms. Warren she agreed with the candidate’s support of Medicare-for-All but was worried that the transition idea would mean higher costs.
“We need to get votes and we need to give people some experiences with it,” Ms. Warren responded.
Ms. Warren’s campaign didn’t reply to a question on how her health plan might have influenced Mr. Sanders’s support. Some of her allies said she didn’t lose support because of the health-care contrast with Mr. Sanders. Instead, they said, the problem arose because she was forced to defend his Medicare-for-All plan before she had worked out the details of her own.
“Let’s be clear: Warren took the most incoming fire when she was defending Bernie’s bill, which even he admits leaves many details unanswered,” said Adam Green, who runs a liberal group backing Ms. Warren.
Aides to rival campaigns acknowledged in December that they had given him a pass on the Medicare-for-All issue and other policies, saying they believed he was unlikely to build a coalition large enough to win the nomination, and his core supporters would never leave him anyway.
“Because of the lack of hits he’s taken, whether from rivals or the media, his negatives have not grown swiftly in recent months in the way you’ve seen from Warren or even Biden,” said Ian Sams, who was an aide in Sen. Kamala Harris’s former campaign.
Mr. Sanders has begun emphasizing personal stories about health care. In the past few months—at Mr. Sanders’s request, aides say—smaller campaign events now almost always include time for people to share their stories, particularly about health care’s high costs. Mr. Sanders repeats some of the more dramatic stories at later events, and his campaign sometimes shares the videos on Facebook and
Twitter.
Sanders aides plan to use a series of recent crises around the world to emphasize his policy consistency. The Vermont senator has long bemoaned U.S. involvement in the Middle East. He has jabbed at former Vice President Biden for voting to authorize the Iraq invasion while a senator in 2002, and pointed out that Mr. Sanders, then a House member, opposed it.
He has stepped up those arguments since President Trump ordered the airstrike that killed Iranian Maj. Gen. Qassem Soleimani. The evening that news broke, Mr. Sanders and aides huddled in a Cedar Rapids, Iowa, hotel, crafting a statement they released just before midnight Eastern time.
By the next morning, they had decided that the candidate, who was on a bus tour through Iowa, needed to address in person what he called an “assassination.” Mr. Sanders spent the morning writing his speech, working on his remarks until he arrived at the event site, the National Motorcycle Museum in Anamosa, Iowa.
Liz Vells, 75, a retiree from Iowa City, said she backed Hillary Clinton in the Iowa caucuses four years ago, even though she liked Mr. Sanders, because she thought Mrs. Clinton more electable. Wearing a “Hindsight is 2020” T-shirt, Ms. Vells said she is fully behind Mr. Sanders this time, a decision she made well before the recent U.S.-Iran confrontation. “He knew that the war in Iraq was a mistake in the early 2000s,” she said.
Mr. Biden has also seized on the lethal airstrike, highlighting his long foreign-policy record and noting that President Obama chose him to serve as the administration’s point person on Iraq. The former vice president’s advisers said the confrontation with Iran has raised the stakes for the primary, adding they would happily put Mr. Biden’s foreign-affairs record up against any other candidate’s.
Some other recent global developments, notably a series of natural disasters in the U.S. and abroad, also can draw voters to Mr. Sanders, his team says.
Images of deadly wildfires in Australia have given candidate Mr. Sanders an opportunity to promote his climate plan. “I think his ideas have caught on,” said Emily Hosmer-Dillard, 33, a Brooklyn, N.Y., resident volunteering for Mr. Sanders in Iowa. She called recent natural disasters “a wake-up call to a lot of people.”.
—Julie Bykowicz and Ken Thomas contributed to this article.
Write to Eliza Collins at eliza.collins@wsj.com.
