COLUMBIA, S.C. — Joseph R. Biden Jr. won the South Carolina primary on Saturday, reviving his listing campaign and establishing himself as the leading candidate to slow Senator Bernie Sanders as the turbulent Democratic race turns to a slew of coast-to-coast contests on Tuesday.
Propelled by an outpouring of support from South Carolina’s African-American voters, Mr. Biden easily overcame a late effort by Mr. Sanders to upset the former vice-president in a state he has long seen as his firewall. His victory will vault Mr. Biden into Super Tuesday, where polls open in just over 48 hours, as the clear alternative to Mr. Sanders for establishment-aligned Democrats.
As much as the results here offered new life to Mr. Biden, the one-time front-runner before he faltered in the fall, they dealt a perhaps fatal blow to the two moderates. Pete Buttigieg and Senator Amy Klobuchar, who had been hoping to overtake Mr. Biden as the candidates of the party’s center, again proved unable to win nonwhite voters.
Perhaps even more consequentially, Mr. Biden’s triumph here also increased pressure on Michael R. Bloomberg to best Mr. Biden in the 15 states and territories voting Tuesday — or consider exiting the race.
For Mr. Biden, though, Saturday night brought a moment to savor.
Low on cash and without a victory in the first three contests, Mr. Biden desperately needed South Carolina, a state for which he has long had a personal affection, to resurrect his third and perhaps final quest for the presidency.
Facing a humiliating fifth-place finish in New Hampshire earlier this month, Mr. Biden flew out of the New England cold before the polls had even closed there and effectively staked his campaign on South Carolina, telling supporters in Columbia that evening that he was counting on the state’s more racially diverse set of voters to offset his dismal showing in the first two, heavily white states.
Then, after finishing a distant second to Mr. Sanders in Nevada, he came directly to South Carolina. He campaigned almost exclusively here while other Democrats fanned out across the much larger map of states that vote Tuesday.
In the debate this week, Mr. Biden promised to win South Carolina and projected confidence that he would prevail with African-Americans.
The results here represented at least an interruption of what loomed as a march to the nomination by Mr. Sanders. South Carolina was the first state where he did not finish at the top, and his distant second to Mr. Biden came after he made a late effort to score a win.
Mr. Biden has led in every poll of South Carolina, but after his Nevada landslide, Mr. Sanders decided to try to deliver a finishing blow against Mr. Biden. Mr. Sanders increased his television advertising in the state and intensified his campaign schedule, with the goal of denying Mr. Biden the chance to reignite his candidacy and perhaps wrapping up the nomination fight by the middle of March.
In South Carolina, Mr. Biden also confronted an unlikely threat in Tom Steyer, a former hedge fund investor from California who poured millions of dollars into courting black voters, and in some cases putting influential state lawmakers on his campaign payroll. But Mr. Steyer appeared to be falling far short of the breakthrough his advisers believed was possible.