As Joe Biden racked up a string of unexpected victories in Super Tuesday primaries, he began to stitch together the kind of political coalition that had eluded his candidacy for months: a broad assembly of voters with the collective power to potentially defeat President Trump in November.

Biden’s strong showing among African-Americans, suburbanites and moderate white voters – spanning geographical regions and drawing from a surge in turnout – boosted confidence among Democrats that the former vice president could soon win a Democratic race that voters have turned into a contest over which candidate is best positioned to beat Trump.

Biden, who won primaries in Texas, Virginia and eight other states on Tuesday, alluded to his burgeoning coalition during his victory speech Tuesday night in Los Angeles.

“Our campaign reflects the diversity of this party and this nation, and that’s how it should be,” he told supporters. “Because we need to bring everybody along, everybody. We want a nominee who will beat Donald Trump, but also keep Nancy Pelosi the speaker of the House, and win back the United States Senate.”

His surprise overnight elevation to delegate leader pleased moderate Democrats and unnerved some Republicans who had expected Vermont Sen. Bernie Sanders, an independent, to come out in front after 14 states voted on Super Tuesday.

The results also harked back to the 2018 midterm elections, in which Democrats won back the House and prevailed in several competitive gubernatorial races by capitalizing on disdain for Trump among moderate and suburban voters, combined with high turnout among members of the Democratic base.

Rep. Joe Cunningham, D-S.C., who flipped a Republican congressional seat in 2018, said Biden’s string of victories was reminiscent of his win in a district containing the suburbs of Charleston.

“A lot of folks who came out and supported us are the same ones who came out and supported him,” said Cunningham, who endorsed Biden.

In a campaign where electability has been a major theme, Biden has taken to calling himself an “Obama-Biden” Democrat and pledging to rebuild the kind of diverse electorate that helped former president Barack Obama secure two terms.

But with Sanders capitalizing on energetic crowds and support from many young voters, Obama’s coalition has not fully rallied behind Biden, said Amy Walter, national editor of the Cook Political Report. While Biden has trailed Sanders among young people and Hispanic voters, he has quickly put together an emerging coalition that capitalizes on the strong anti-Trump sentiment among black voters and suburban women, she said.

“Every campaign should have its own coalition that is organic for the candidate and is the right coalition for the moment,” Walter said. “These suburban voters who in years past would split their votes more evenly between Democrats and Republicans, are now coming out overwhelmingly against Trump.”

Virginia, where voters showed up in record numbers for Tuesday’s primary, is a case in point.

Roughly 1.3 million Virginia voters cast ballots, about 21 percent of the electorate, according to an analysis of unofficial results by the nonpartisan Virginia Public Access Project. That’s up from the previous record of about 986,000 votes and 18 percent of the electorate in 2008, when Obama was challenging Hillary Clinton for the party’s nomination.

“The interest … in defeating Donald Trump is so intense that it’s almost unprecedented,” Richmond political scientist Bob Holsworth said.

Biden was the beneficiary of the Virginia groundswell, easily beating Sanders and three other hopefuls.

“It’s just extraordinary. In the commonwealth of Virginia, folks are fired up. They want to beat Trump,” former governor Terry McAuliffe, a Democrat, said in an interview. He pointed to massive jumps in turnout in the once-purple District of Columbia suburbs, which he said reflected “the intensity of the anti-Trump feeling in northern Virginia.”

Cities with large African-American populations also registered strong gains, with black voters accounting for a quarter of all ballots cast.

Biden also prevailed in Minnesota, Massachusetts and across the South, building on a swift-moving series of events in which two of his main moderate challengers dropped out of the race and endorsed him before Tuesday.

The endorsements by former South Bend, Indiana, mayor Pete Buttigieg, a Democrat, and Sen. Amy Klobuchar, D-Minn., combined with Biden’s resounding win Saturday in South Carolina, had an impact. Voters who decided late heavily backed Biden, according to exit poll results.

While Biden came away from Tuesday’s primaries with the most delegates, the contests revealed some of the challenges he faces as he tries to secure the nomination and pull together a fractured party.

He was trailing to Sanders in the country’s most populous state, California, as votes were still being counted, and continues to lag with Hispanics and younger voters. It’s also not clear how Biden would win over the liberal wing of the party, which has supported Sanders’ agenda advocating more sweeping changes.

But Biden’s victories also brought into sharper relief Sanders’ failure to deliver on his pledge to drive a surge in turnout among young people and disaffected voters he claimed would power his campaign to a revolution-style victory.

Sanders on Tuesday acknowledged that he was disappointed in the turnout figures.

“I will be honest with you, we have not done as well in bringing young people into the political process,” he told reporters in Burlington, Vermont. “It is not easy.”

According to exit polls, about 1 in 8 voters in Super Tuesday states were 18- to 29-year-olds, compared to 3 in 10 who were 65 or older.

Republicans were quick to point out that Biden entered the race last year as a presumed leader, only to falter due to uneven performances on the campaign trail and lackluster fundraising.

“Just a few days ago, Democrats had left Joe Biden for dead because they realized he was a terrible candidate. Nothing has changed,” said Trump campaign spokesman Tim Murtaugh. “He’s still a terrible candidate and we still don’t know if he’ll be President Trump’s opponent.”

Trump and his campaign have sought to interfere with the Democrats’ primary, openly pushing for a protracted fight between the party’s liberal and moderate wings that could last through the nominating convention in July.

Sanders said Tuesday he planned to move forward with his campaign, and attacked Biden as a member of the “establishment” who has voted for bad trade deals.

A drawn out Democratic battle over delegates and party rules would allow Trump to continue his attempts to build his coalition ahead of the general election. Trump, who spoke to the Latino Coalition Legislative Summit on Wednesday, has been making a public appeal to minority voters to back his campaign.

Some younger Latino voters, who have backed Sanders overwhelmingly, distrust Biden because of the high number of deportations that took place during the Obama administration, said Stephen Nuño-Perez of Latino Decisions, a nonpartisan polling firm that focuses on Latino political and social attitudes and that has done work for Democratic organizations.

Exit polling suggested that Biden won the votes of roughly 70 percent of black voters in Virginia and Alabama, and did nearly as well in North Carolina and Texas, getting roughly 60 percent of the vote. Biden also won in Tennessee, Oklahoma and Arkansas.

Darren Peters, who worked on the presidential campaigns of Bill and Hillary Clinton, said Biden’s strong showing with black voters in Southern states could help him if he becomes the party’s nominee.

“It shows an ability to galvanize the kinds of constituencies that are going to be needed to win in a general election,” he said, highlighting the importance of the black vote in key swing states like Pennsylvania and Michigan.

While some Democrats have wondered if Biden, a familiar face with a long track record, would lose in the same way as Hillary Clinton, Biden drew broader support in North Carolina and Virginia than Clinton did in 2016. Clinton won 86 percent of Virginia precincts and 65 percent of North Carolina precincts in 2016. Biden won 93 percent of precincts in both states.

Rep. Tim Ryan, D-Ohio, who ended his presidential bid last year, said Trump should be nervous about Biden’s ability to “connect with the Whole Foods moms and the suburban women” who may have voted Republican in the past but have been turned off by the president’s divisiveness.

“I think there’s a silent majority of people who want Donald Trump out of office,” he said. “They don’t want to have heated discussions with people about it. They don’t want to get in fights with people about it. They don’t want to be on social media about it, but they’re appalled at his behavior.”