Voter turnout in the Democratic presidential primaries in Michigan, Missouri and Mississippi reached its highest levels in more than a decade on Tuesday.

The surge in turnout was largely driven by black voters, moderates and suburbanites, who have come out in force in recent weeks to the benefit of former Vice President Joe Biden Joe BidenSenate Republicans face tough decision on replacing Ginsburg What Senate Republicans have said about election-year Supreme Court vacancies Biden says Ginsburg successor should be picked by candidate who wins on Nov. 3 MORE.

That trend began in South Carolina late last month and has served to lift Biden’s campaign up from the brink of collapse and deliver him a spate of wins in the primary race.

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In Michigan, Democratic turnout shattered records on Tuesday, with nearly 1.6 million voters casting ballots in the primary — a nearly 33 percent increase over 2016 when just shy of 1.2 million votes were recorded.

Biden beat Sen. Bernie Sanders Bernie SandersKenosha will be a good bellwether in 2020 Biden's fiscal program: What is the likely market impact? McConnell accuses Democrats of sowing division by 'downplaying progress' on election security MORE (I-Vt.) in Michigan, dealing a crushing blow to his chief progressive rival, who carried the state over Hillary Clinton Hillary Diane Rodham ClintonWhat Senate Republicans have said about election-year Supreme Court vacancies Bipartisan praise pours in after Ginsburg's death Trump carries on with rally, unaware of Ginsburg's death MORE four years ago.

For Democrats more broadly, the high turnout in Michigan was a promising development at a time when they are looking to recapture parts of the Midwest that they lost to President Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE in 2016.

Lavora Barnes, the chairwoman of the Michigan Democratic Party, labeled the surge in her state as a “turnout explosion” ignited by widespread opposition to Trump.

“From his attacks on health care and access to clean water to his failure to grow manufacturing jobs in our state, Donald Trump has broken promise after promise to Michigan and yesterday, Democratic voters showed they’re ready to hold him accountable for that fact,” Barnes said in a statement.

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In Mississippi, turnout swelled by about 19 percent over 2016 levels, according to the most recent vote tallies. In Missouri, the increase in turnout was a more modest 5 percent over where it was four years ago. Biden carried both of those states on Tuesday.

Turnout in North Dakota’s Democratic caucuses quadrupled from 2016, surging from less than 3,400 four years ago to nearly 15,000 on Tuesday. The state implemented new caucus rules that effectively made it run more like a primary.

The two other states that held primaries on Tuesday, Washington and Idaho, also saw massive increases in Democratic votes cast, though it’s difficult to compare turnout to prior years, because both states switched from caucuses to primary systems, which typically drive higher turnout.

For Sanders, Tuesday’s nominating contests marked another disappointment.

He ultimately won the North Dakota Democratic caucuses and ongoing tallies in Washington show him with a slight lead over Biden.

But his defeat in Michigan, where he had hoped to revitalize his candidacy after a series of losses on Super Tuesday, undercut his argument that his populist message and calls for sweeping political and economic change would resonate with working class voters in the industrial Midwest and help Democrats win Michigan in November.

It also provided further evidence of the challenge Sanders faces in turning out younger voters at higher rates. He won twice as much support among 18- to 44-year-olds as Biden did in Michigan. But those voters made up only about 38 percent of the primary electorate, down from 45 percent in 2016.

Voters 45 and older, meanwhile, accounted for roughly 62 percent of the Democratic electorate in Michigan on Tuesday. Two-thirds of those voters backed Biden in the primary, according to exit polling.

The broader election results on Tuesday also underscored Sanders’s lingering struggles to win the support of black voters, the Democratic Party’s most loyal constituency. He lost those voters to Biden by wide margins in Michigan, Missouri and Mississippi, where black voters made about 70 percent of the primary electorate.

Speaking to reporters in his hometown of Burlington, Vt., on Wednesday, Sanders delivered a sober assessment of his campaign. He said that while he was winning the “ideological debate” in the Democratic primary, he was losing the “debate over electability,” noting that many voters had chosen to support Biden because they see him as the candidate best able to beat Trump.

But he also touted his strong support among young voters, saying that he was winning the “generational debate” in the primary race.

“While Joe Biden continues to do very well with older Americans, especially those people over 65, our campaign continues to win the vast majority of the votes of younger people,” Sanders said. “And I am talking about people not just in their 20s, but in their 30s and in their 40s. The younger generations of this country continue in very strong numbers to support our campaign.”