Finally! Four states and nearly two months into the Democratic primary voting, Joe Biden scored a win. On Saturday, he received a big electoral kiss from South Carolina, where he captured 48 percent of the vote and at least 29 of 54 delegates (with more expected as the results were finalized). It was the largest margin of victory — and the largest single delegate haul — in the race thus far.

Bernie Sanders, the presumptive front-runner, placed a distant second with 20 percent. Tom Steyer, who had bet everything on the state, came in third with 11 percent — a weak enough showing that he promptly, and sensibly, ended his campaign. No one else made much of a ripple.

South Carolina was the first major test with African-American voters, who make up some 60 percent of the state’s Democratic electorate. It was not a surprise that Mr. Biden won. Black voters are the rock upon which his candidacy rests. But no one expected a win this big — perhaps not even the candidate. Mr. Biden carried every county, with a strong showing among women, older voters, moderates and conservatives, along with 60 percent of the black vote. Turnout topped 500,000, compared to around 370,000 in 2016.

Beaming, Mr. Biden delivered a cri de coeur. “This is a battle for the soul of the United States of America,” he said. “Winning means uniting America, not sowing more division and anger. It means not only fighting but healing the country.” He spoke about grief and faith and his belief in the nation’s goodness. He took an oblique poke at Mr. Sanders. “Talk is cheap, false promises are deceptive, and talk about revolution isn’t changing anyone’s life.” And he dangled the promise of a return to decency and sanity. “We can believe again. We’re better than this moment. We’re better than this president! So get up! Take back our country!” It was Mr. Biden at his best, passionate and personal. If he had looked half this good in any of the debates, this might have been a very different race.