FALLS CHURCH, Va. — They were disaffected Republicans in affluent Washington suburbs. They were shipyard employees in Norfolk. And they were health care workers in Petersburg.
They all came together on Super Tuesday in an extraordinary surge to the polls in Virginia, propelling former Vice President Joseph R. Biden Jr. to an overwhelming victory in a state that just days earlier had seemed up for grabs. The triumph was part of a 10-state sweep for Mr. Biden that resurrected his presidential candidacy, and established him as the centrist Democrat who would go head-to-head with Senator Bernie Sanders of Vermont, the standard-bearer of the party’s liberal wing.
In Virginia on Tuesday, it was no contest. Mr. Biden won with 53 percent of the vote, 30 percentage points more than Mr. Sanders. Voter turnout broke a state record for a presidential primary, and was especially high in suburban areas near Washington and near Richmond and Norfolk, as well as in regions with large African-American populations. Petersburg, a mostly-black city south of Richmond, went 75 percent for the former vice president.
The range of support suggested Mr. Biden had the potential to put together a broad coalition across categories of race, gender and age that could be a potent weapon in a race against President Trump.
Former Gov. Terry McAuliffe of Virginia attributed Democratic turnout in the state to deep disgust with the Trump presidency among Democrats and moderate Republicans.
“We have to give tremendous credit to Donald Trump,” Mr. McAuliffe said. “He has been the single biggest driver to the Democratic Party of Virginia. There are a lot of like-minded Republicans who said, ‘I can’t vote for Trump but you got to give me somebody who we can vote for.’ Biden was always at the top of that list.”
That was the motivation for Laura Bligh, a 39-year-old personal trainer from Falls Church. She had planned to back Senator Elizabeth Warren of Massachusetts, but said she changed her mind on Monday and voted for Mr. Biden.
“My number one priority is to beat Trump and that seemed like the best chance to do it,” Ms. Bligh said while waiting to pick up her daughter outside Shrevewood Elementary in Falls Church on Wednesday afternoon. “When there was still a large pool of candidates, minority options still had a chance.”
Ms. Bligh said she considered her vote not just a repudiation of Mr. Trump, but an effort to block Mr. Sanders, who she predicted would lose in a bid against the president.
In Virginia, exit polls show that Mr. Biden dominated across gender, race and educational lines. He had support from men and women, white and black people, college graduates and non-graduates alike by double-digit margins over Mr. Sanders. In fact, in most of the demographic categories that Mr. Biden won, his share of the vote was larger than Mr. Sanders’s and Ms. Warren’s combined.
Even more significantly, Mr. Biden made major inroads among Mr. Sanders’s core constituencies. For instance, Hispanic voters — who went overwhelmingly for Mr. Sanders in the Nevada caucuses — actually went for Mr. Biden by about 13 percentage points in the Virginia primary. And even among voters who described themselves as very liberal, Mr. Sanders won by only about 4 percentage points.
The only major demographic group that Mr. Sanders won in Virginia was young voters.
Mr. Biden’s triumph here was clearly aided by his romp in the South Carolina primary on Saturday, and a string of endorsements from prominent Democratic politicians in Virginia — Senator Tim Kaine, Representative Bobby Scott and Mr. McAuliffe among them.
Exit polls also showed that Virginia voters coalesced around Mr. Biden’s candidacy practically overnight. Nearly half said they made up their minds in the final days before Tuesday’s contest, with two-thirds of those voters picking Mr. Biden.
The move to Mr. Biden was so swift and pronounced that his allies were claiming for their candidate the kind of surge in new voters that Mr. Sanders himself has promised but failed to deliver.
“The blue wave voters who flipped the House in 2018 and made Nancy Pelosi the speaker of the House, they really turned out in large numbers last night, and we overwhelmingly won their support,” said Mayor Eric Garcetti of Los Angeles, a national co-chairman of Mr. Biden’s campaign.
In a conference call with reporters, Mr. Garcetti cited turnout increases of 76 percent in three Virginia congressional districts that include parts of Norfolk and the suburbs of Washington and Richmond.
Over all, 1.3 million voters in Virginia went to the polls on Tuesday, surpassing the votes cast in 2016 by nearly 70 percent and, even more stunningly, breaking a previous Democratic record of 986,000 votes set in 2008, when Barack Obama was on the ballot.
Democratic turnout on Tuesday was up broadly compared with 2016 — with Texas up 49 percent, Tennessee up 38 percent, and Vermont and North Carolina both increasing by 16 percent. Several states that had switched from caucuses to primaries this year — Colorado, Maine, Minnesota and Utah — also saw heavy increases in participation.
Nowhere was the Democratic boom more pronounced than in the tony Northern Virginia suburbs of Washington. Here, among the million-dollar homes populated by lobbyists, corporate lawyers and employees of government contractors, Mr. Biden ran up huge margins over Mr. Sanders and the rest of the Democratic field while turnout in some areas nearly doubled from the party’s 2016 primary.
The region, with its high population of educated professionals, was believed to be a good area for Ms. Warren and Pete Buttigieg, the former mayor of South Bend, Ind., before he ended his campaign on Sunday night.
Dan Helmer, who in November ousted the last remaining Fairfax County Republican in the Virginia General Assembly, said the rush of new voters helped catapult him into office. His victory, completing the Democratic sweep of the Washington suburbs, came after Mr. Trump alienated many of the federal workers and contractors.
“He has converted huge numbers of federal civil servants to Democrats,” said Mr. Helmer, who switched his support from Mr. Buttigieg to Mr. Biden on Monday. “It’s a pocketbook issue for Northern Virginia. Trump has just shook the earth in a way that it’s going to take years for Republicans to recover.”
The Falls Church precinct that voted at Shrevewood Elementary School, steps from a popular cycling trail that some commuters use to get to work in the capital, drew nearly twice as many voters on Tuesday as it did for the 2016 contest between Mr. Sanders and Hillary Clinton. Mrs. Clinton’s margin over Mr. Sanders’s in 2016 in that precinct was 99 votes; Mr. Biden beat Mr. Sanders by 250 votes.
For Sanders supporters, watching the turnout surge he had promised go to Mr. Biden served as a particularly bitter disappointment. They attributed the Vermont senator’s weak showing in the suburbs to moderate Democrats’ coalescing around Mr. Biden faster than progressives did behind Mr. Sanders — though in Fairfax County, Michael R. Bloomberg, the former mayor of New York, won more votes than did Ms. Warren. They also cited the rapid nationalization of a race they had hoped to win through on-the-ground organizing.
“Bernie Sanders, he reached out to Latino voters, Muslims, Arab-American — these were constituencies that he had a significant amount of support here,” said Yasmine Taeb, a Sanders-aligned Democratic National Committee member from Falls Church. “While there was an increase in the number of young voters and minority voters, it still didn’t match up to the older white voters that you traditionally see voting in primaries.”
Jonathan Sokolow, a labor lawyer who is co-chairman of the Sanders campaign in Virginia, said the results in Virginia and elsewhere were not an indication that Mr. Sanders did not have wide support in the party.
“I don’t think it’s correct to say that we don’t have majority support,” Mr. Sokolow said. “We’re fighting to see who is the best candidate to defeat Donald Trump.”
But across the Virginia suburbs, Mr. Sanders’s argument fell flat in the face of Mr. Biden’s late strength.
Marcus Simon, a Democrat who represents Falls Church in the Virginia House of Delegates, said he voted early on Saturday for Ms. Warren. By Tuesday, he had changed his mind, and encouraged his wife to vote for Mr. Biden.
“Electability is something everybody is thinking about and who has the best chance of defeating Trump,” he said. “The idea of risking the nomination to somebody like Bernie Sanders, the concern would be that he wouldn’t have the broad appeal to defeat Donald Trump.”
Tucker Martin, who a decade ago was a top aide to former Gov. Bob McDonnell, Republican of Virginia, appears to fit into this category. Mr. Martin considers himself a Republican, but on Super Tuesday, he cast a ballot for Mr. Biden.
“I am a Never Trumper and I’m out of partisan politics,” Mr. Martin said on Wednesday. “I think for many voters in Virginia, Joe Biden may represent a safe place to go to register their dislike for the current occupant of the White House.”
Maggie Astor and Thomas Kaplan contributed reporting from New York.