Biden Wins His First Primary in South Carolina, Where His 2020 Victory Began

President Biden won the South Carolina primary on Saturday, giving him the kind of emphatic result he no doubt envisioned when he made the state the first contest on the Democrats’ presidential nominating calendar.

The election, called by The Associated Press shortly after polls closed, gives Mr. Biden the first set of delegates required to claim the Democratic nomination at the party’s convention in August.

Mr. Biden vowed that South Carolina would once again send him to the White House.

“The people of South Carolina have spoken again, and I have no doubt that you have set us on the path to winning the presidency again — and making Donald Trump a loser again,” the president said in a statement released by his campaign.

Mr. Biden won an overwhelming majority of South Carolina Democrats, more than 96 percent with 80 percent of the vote counted — dominating every county with more than 95 percent of the vote, including in heavily Black areas.

His campaign had wanted South Carolina to prove that the party’s base — particularly Black voters — remain devoted to Mr. Biden and would turn out for him in large numbers. The state’s open primary system means voters are free to choose which primary to vote in, and the stakes are far higher in the Republican contest pitting Mr. Trump against Nikki Haley, the former South Carolina governor — and there had been some concern from party officials about voters waiting to participate in that contest on Feb. 24 instead.

Black voters are critical to Mr. Biden’s success in battleground states, but transposing South Carolina’s results in February to November voting in Detroit, Milwaukee and Philadelphia is a tricky proposition, given that Saturday’s primary was viewed by most observers — correctly, as it turned out — as noncompetitive.

The primary was on pace to have about 150,000 votes, at the low end of the primary eve projection from Representative James E. Clyburn, Mr. Biden’s most important South Carolina surrogate whose 2020 endorsement helped propel him to the nomination that year. The Biden campaign itself studiously avoided making public predictions about how many Democrats would vote in Saturday’s primary.

There is little data to measure Saturday’s Democratic turnout against.

The last time an incumbent Democratic president sought re-election, in 2012, President Barack Obama went unchallenged in South Carolina — and the state did not hold a primary.

Four years later, when former Secretary of State Hillary Clinton defeated Senator Bernie Sanders of Vermont in the state’s primary, 370,864 people voted. In 2020, with no competitive Republican primary and 12 Democrats on the ballot, 536,949 people voted.

The South Carolina Democratic Party said early vote data showed that the share of Black voters in the electorate was 13 percent higher than in 2020, when people of color made up about half of the voters in the Democratic primary and there was no Republican primary to siphon off voters.

In 2016, the last year in which both parties held presidential primaries in South Carolina, voters of color made up two-thirds of Democratic primary voters.

Christale Spain, the chair of South Carolina’s Democratic Party, spearheaded much of the state party’s organizing operation. Late Saturday, she said she felt “very encouraged” by the state’s early vote numbers, which showed that more than 51,000 voters cast early Democratic primary ballots. She also added a caveat about voters’ excitement for Mr. Biden.

“We might not see that enthusiasm, but they are mission-driven,” she said of South Carolina’s Democrats. “They know that this is a choice between progress and regression and freedom and anti-freedom.”

By moving South Carolina from the party’s fourth contest to its first, Mr. Biden elevated the influence of Black voters in choosing the Democratic nominee and insulated himself from potential primary challengers in a state that saved his 2020 campaign and propelled him to the White House.

There was not much drama Saturday night. Within 30 minutes of polls closing, The Associated Press called the primary for Mr. Biden, his campaign distributed his victory statement and a watch party hosted by the South Carolina Democratic Party in Columbia began to close down.

Unlike in New Hampshire, where a Biden challenger — Representative Dean Phillips of Minnesota — spent millions on his campaign, the president had South Carolina virtually all to himself. The state’s voters provided only trace amounts of support for Mr. Phillips and Marianne Williamson, the author who also ran a quixotic presidential campaign in 2020.

About 64 percent of New Hampshire Democratic voters wrote Mr. Biden’s name in on the ballot, adding to the evidence that the party’s base is behind him.

The Biden campaign had treated South Carolina’s primary as an important contest even though the Republican-leaning state is unlikely to be a general-election battleground. The campaign hired four paid staff members in the state — devoting resources to a noncompetitive state before it does in general-election battlegrounds like Arizona and Pennsylvania. And the South Carolina Democratic Party spent months working to drive up turnout to keep its new spot in the primary calendar.

In a news conference after the race was called for Mr. Biden, the chair of the Democratic National Committee, Jaime Harrison, a South Carolina native, said he was “extremely ecstatic” about turnout numbers.

Mr. Clyburn, who refrained in his speech on Saturday from any analysis of turnout numbers that had been posted so far, argued that Mr. Biden’s win had implications beyond South Carolina.

“This is about keeping this country on its track to a more perfect union,” he said to applause.

At the end of the night, both Ms. Spain and Mr. Harrison expressed confidence that South Carolina would keep its first-in-the-nation status for the Democrats.

“What’s the state motto, ‘While I breathe I hope’?” Mr. Harrison said. “I’m going to do everything in my power to make sure.”