Now some who worked on the front lines of his campaign, including black staffers and surrogates, are speaking out about what they believe was a negligent strategy that underestimated the significance of the first primary with a majority-black electorate — a blueprint they said they tried and failed to redirect, and one that ultimately put the campaign on a devastating trajectory.

Sanders sees the United States through the prism of class, but the 2020 primary has in some ways reaffirmed that for many Americans, the racial divide is more urgent. The senator built a coalition of millennials, working-class whites and Latinos, wagering that a strong showing in the first three states — none of which has many black voters — would power him through South Carolina and beyond.

As a result, many African Americans felt disconnected from him. “I think the distinguishing attitude for Sanders, that you didn’t see associated with Biden, was an angry white man,” said Ivory Thigpen, a state representative who served as co-chair for Sanders in South Carolina and believes strongly in his message. “In the African American culture,” he said, “nonverbal communication and body language is huge.”

Conveying a personal touch was never Sanders’s strength, Thigpen added. But he added, “I think being accessible would have made up for it.”