In his campaign announcement, Mr. Biden made no secret of the importance of Black voters to his re-election. The Biden allies with the most airtime in his three-minute video, aside from his wife, were Vice President Kamala Harris, Justice Ketanji Brown Jackson and the Rev. Al Sharpton.

“I have not found a lack of enthusiasm,” said Representative James E. Clyburn of South Carolina, who was Mr. Biden’s most important Black surrogate in 2020. “I just haven’t found it. And people keep saying it. But it’s not there.”

On Friday, Mr. Clyburn’s annual fish fry, which brings together candidates and hundreds of South Carolina Democrats, offered an early look at that enthusiasm. The state party is preparing to hold its presidential primary first in the nominating process — a move Mr. Biden and Democrats said was made to give Black voters more influence.

Mr. Biden’s allies maintain that his administration has delivered for Black voters but that he has failed to trumpet some of his progress. Since taking office, he has provided billions of dollars for historically Black colleges and universities, and he has appointed more Black judges, including Justice Jackson, to the federal bench than any other president. Black unemployment is at a record low. The economy, a top concern for Black voters, has recovered from its pandemic doldrums, though inflation, which spiked last summer, remains higher on a sustained basis than it has been for decades.

“The president and vice president have made issues Black Americans care most about a priority and are running to finish the job,” said Kevin Munoz, a spokesman for Mr. Biden’s campaign. “The campaign will work hard to earn every vote and expand on its winning 2020 coalition.”