Clyburn is the highest ranking African American in Congress has long been close with Biden and has been open about his affinity for the former vice president during the Democratic primary.

But Biden started to see his support erode in South Carolina as Sanders surged. And lawmakers like Clyburn started to grow increasingly nervous that Sanders, a self-described democratic socialist, would be a drag on the ticket and turn off moderate whites as well as African-American voters, who could account for two-thirds of the ballots cast in Saturday’s primary.

“I do believe it will be an extra burden for us to have to carry. This is South Carolina, and South Carolinians are pretty leery about that title socialist,” Clyburn said Sunday on ABC’s This Week.

Clyburn’s sentiment is widely shared by others in the Congressional Black Caucus, whose members have been more likely to endorse Biden — the loyal vice president to the nation’s first black president — than any other candidate in the race.

The concern about Sanders among lawmakers on the ground in South Carolina is “palpable,” according to one member of the black caucus who did not want to publicly criticize Sanders, the current Democratic frontrunner.

Black lawmakers who have endorsed different candidates have attended many of the same events this week in South Carolina and have grown increasingly concerned about Sanders, the black caucus member said. But they’re not ready to publicly speak out against the Vermont senator until Super Tuesday to see if any challengers to Sanders are viable, the black caucus member said.

On Wednesday, Clyburn echoed Biden's frequent assertions that the country is at an "inflection point."

“We don't need to make this country great again. This country is great. That's not what our challenge is,” he argued.

”Our challenge is making the greatness of this country accessible and affordable for all,” he continued, adding that “nobody with whom I've ever worked in public life is any more committed to that motto, that pledge that I have to my constituents, than Joe Biden.”

He said Wednesday that he’d made the decision to publicly endorse Biden after an elderly constituent implored him to speak out at the funeral of his accountant last week.

“‘I've been waiting to hear from you. I need to hear from you. This community wants to hear from you,’” Clyburn said the constituent told him. “I decided then and there that I would not stay silent.”

But he also invoked his late wife Emily who died last fall, saying that there was no leader she loved more than Biden. Clyburn continued that he had gotten to know the former vice president decades earlier through his work during the civil rights movement.

"I know Joe. We know Joe. But most importantly, Joe knows us," Clyburn said.

Laura Barrón-López contributed to this report.