Biden’s stunning vault over both Warren and Senator Bernie Sanders of Vermont on Tuesday, as projected by the Associated Press, followed days of polling showing the two progressive senators in a close contest. His Massachusetts surge mirrored his remarkable sweep through more than half of the 14 Super Tuesday states, a performance sparked by a strong showing in South Carolina last weekend and a rapidly evolving field.

Former vice president Joe Biden, floundering just days ago amid a crowded Democratic field, pulled off a surprise victory in the Massachusetts primary, delivering a humbling defeat to Senator Elizabeth Warren in her home state.


With 88 percent of precincts reporting at 1 a.m. Wednesday, Biden, who entered Super Tuesday with a fresh round of endorsements and momentum, led with 34 percent. Sanders had 27 percent, and Warren trailed with 21 percent.

The race transformed in the 48 hours before polls opened here, first with the departures of former South Bend, Ind., Mayor Pete Buttigieg and Senator Amy Klobuchar of Minnesota and then with their and other prominent Democrats’ quick backing of the former vice president as the primary alternative to Sanders.

For many in Massachusetts’ affluent and blue-collar suburbs, Biden also became their choice in the quickly narrowing field — despite the presence on the ballot of their twice-elected senior senator, who had not campaigned here since Dec. 31.

According to unofficial results, Warren held on to liberal pockets like Somerville and Brookline. But Biden cleaned up in the well-to-do suburbs like Wellesley and Newton, and ran up big margins in working class areas such as Brockton and Randolph.

“People here believe in Joe. And I think the underlining thing is that you can’t make people go where they don’t want to go,” said Larry Rasky, a Boston-based political consultant who is helping run the super PAC backing Biden.


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The vice president’s reemergence, he said, has also prompted a surge in donors “who want to play a bigger role” going forward. “We spend money as fast we can raise it,” Rasky said, adding that attention now turns to upcoming states like Michigan and Washington.

Losing Massachusetts is a painful setback for Warren, and is certain to intensify questions about why the Cambridge Democrat remains in the race if she hasn’t won anywhere — even at home. She earned the ignominy of becoming the first major presidential candidate from Massachusetts to lose their home state’s primary in the 60 years since John F. Kennedy easily captured the win here in 1960.

Former New York City mayor and billionaire Mike Bloomberg, despite dumping truckloads of cash into the race in Massachusetts, was still below the 15 percent threshold needed to win a portion of the state’s 91 pledged delegates. He was reportedly reassessing his campaign’s prospects after disappointing finishes in Super Tuesday states.

CNN exit polling indicated that 51 percent of Massachusetts Democratic primary voters made up their minds in the last few days, and Biden won more of those late-deciders than any other candidate — 43 percent.

Meanwhile, former governor William F. Weld lost the Republican primary to President Trump.

As early results came in, the handful of Biden supporters gathered in the basement of The Fours in Quincy let out cheers and war cries when the flat screens in the corner showed him posting strong results. Practically surrounded by press, whose numbers doubled their own, the party attendees were wowed that their candidate was doing so well. They credited his success to his personality and charisma.


When the Associated Press called the race for Biden, the party exploded into screaming, hugs, and chants of “Let’s go, Joe!”

“I know that when you spend time with Joe Biden not only do you love him as a man but you respect his remarkable record of public service,” said Rufus Gifford, a former ambassador to Denmark under President Barack Obama who served as finance director for Obama’s 2012 reelection campaign.

“Biden gives me hope," said Mo Zaidan, 19, who is studying finance and accounting at Suffolk University. "He gives me someone who can unify the country.”

Sanders, 78, made a strong play to win Massachusetts — and the biggest share of the state’s delegates — hosting two rallies on either side of the state that drew thousands over the weekend. It was a show of force that analysts read as both an effort to amass as many delegates as possible Tuesday but also to make a point that Warren is not a viable presidential candidate.

Warren, for her part, chose not to spend time campaigning in her home state, instead relying on surrogates to rally her volunteers and supporters in recent days.

Warren’s campaign also appeared to be protecting against the possibility of an embarrassing night. The 70-year-old former Harvard law professor did not stick around for a “victory” party, flying instead to Detroit for a rally in a state where voters don’t go to the polls until next week.


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The events her campaign held Tuesday in Massachusetts were closed to the press, a rarity on the trail. Neither Sanders nor Biden themselves were in Massachusetts, but opened their "watch” parties in Boston and Quincy, respectively, to the public and reporters.

More than 70 Sanders supporters crammed into a back room at Democracy Brewing in Downtown Crossing, where they watched results roll in from CNN on a projection screen while sipping hazy IPAs and chomping on plates of fries.

At one point, the room burst into applause when early reports showed Sanders leading in Texas, only for the cheers to quickly fade when initial numbers from Massachusetts popped on the screen — showing Biden on top.

“What?!” someone yelled from the crowd.

“I consider everything a must-win for him,” Derek Murphy, a 27-year-old graphic designer from Brighton, said of Sanders as he watched the TV and checked his phone. “It’s really strange how over the weekend there were so many changes.”

Murphy said he had considered Warren, too, but felt she had compromised on big policies, particularly Medicare for All once she began laying out details of how she would try to implement it.

“That was definitely the turning point,” he said.

Nonetheless, hundreds of supporters greeted Warren like a returning hero in Cambridge on Tuesday morning, lining the sidewalks for blocks to cheer the liberal firebrand, her husband, Bruce H. Mann, and their golden retriever, Bailey, as they made their way to their local polling site.


She shook hands, embraced people, and stopped for selfies. At one point, the crowd chanted, “I am a Warren Democrat.”

But Warren’s third-place finish will make her an asterisk in the modern history of Massachusetts presidential contenders: Edward M. Kennedy (1980), Michael Dukakis (1988), Paul Tsongas (1992), John Kerry (2004), and Mitt Romney (2008 and 2012) all won the Massachusetts primary, with three of them — Dukakis, Kerry, and Romney in 2012 — ultimately winning his party’s nomination.

(The Brookline-born Robert F. Kennedy lost the Massachusetts Democratic primary in 1968 to Eugene McCarthy, but Kennedy was then a senator from New York.)

“I’m not worried,” Warren said after voting for herself Tuesday morning, when asked about the prospect of losing her home state. “I am happy to be part of this Democratic process.”

But Warren supporters still had plenty of enthusiasm about her candidacy.

Mal Malme, a 54-year-old theater artist and performer from Cambridge, called Warren a uniter, someone who has “a genuine vision to make this world more equitable and fair for everybody,” and said the country needs someone in the White House “who is not a racist, who is not a bully.”

“I feel like she has my back," said Arielle Scoglio, 31, a graduate student at Northeastern. "In the primaries I wanted to vote for who I like rather than who I think could win a presidential election necessarily.”

Other voters followed their heads, even though their hearts were with Warren.

“I wanted to vote Warren. I just don’t think she’s going to beat Trump,” said Brian Cheney, 28, of Cambridge, who backed Sanders instead. He likes the Vermont senator’s health care plan, but not all of his policy positions. "It seems like he’s got a much bigger backing right now going into it.”

For many voters, the decision came down to pragmatism rather than inspiration.

In Milton, Travis and Quin Robertson brought their 4-year-old daughter with them to the town’s senior center as they both reluctantly voted for the 77-year-old Biden. It was a decision they had made only the night before.

“The pendulum went so far right with Trump, and Bernie’s just so far left that we settled for the middle," said Travis. "Which is vanilla pudding.”

Stephanie Ebbert, Danny McDonald, and Katie Johnston of the Globe staff and Globe correspondent Meghan Sorensen contributed to this report.

Victoria McGrane can be reached at victoria.mcgrane@globe.com. Follow her on Twitter @vgmac. Matt Stout can be reached at matt.stout@globe.com. Follow him on Twitter @mattpstout