This is exaggerated. Mr. Biden is correct that in most polls, he leads Democratic candidates among black voters overall, but he is wrong to deny Senator Bernie Sanders’ edge with younger African Americans.

A January poll conducted by The Washington Post and Ipsos, a nonpartisan research firm, found that Mr. Biden held a wide lead among black Democrats with 48 percent support, but Mr. Sanders led with those between age 18 and 34 at 42 percent while Mr. Biden placed second at 30 percent.

An Ipsos survey conducted with Vice this month asked black Americans who they would consider voting for and found that 56 percent would consider voting for Mr. Sanders and 54 percent for Mr. Biden, a statistical tie. Among those between ages 18 and 34, Mr. Sanders’ support increased to 81 percent compared with 65 percent for Mr. Biden, according to a breakdown provided by Chris Jackson, the vice president of Ipsos Public Affairs.

In a poll by the political action committee BlackPac and released in December, Mr. Biden led all black voters with 38 percent, but trailed Mr. Sanders in support among black voters between ages 18 and 24 at 14 percent compared to 30 percent for Mr. Sanders. Support for the two candidates was nearly identical among black voters between the ages of 25 and 39, with 24 percent supporting Mr. Biden and 25 percent supporting Mr. Sanders.

The Sanders campaign also pointed to an array of surveys demonstrating the same generational gap: a fall poll from Harvard Kennedy School’s Institute of Politics where Mr. Sanders was the first choice of black voters between ages 18 and 29, a January poll from the Chegg/College Pulse Student Election Tracker where Mr. Sanders led with black college students with 43 percent and a September survey from Essence Magazine where Mr. Sanders had the most support of black women between ages 18 and 34 with 19 percent.

What Was Said

“I was involved in the civil rights movement.”

— at the Brown & Black forum

This is exaggerated. Over his long political career, Mr. Biden has occasionally suggested he played a greater role in the civil rights movement of the 1960s than he actually did. While there are accounts of Mr. Biden participating in a few desegregation events, he has also said he would not consider himself an activist in the movement.

Mr. Biden has said that he protested a segregated movie theater in demonstrations in Wilmington, Del. at the Rialto Theater in the early 1960s. His account is backed by a former president of the state chapter of the National Association for the Advancement of Colored People and a former president of the Delaware A.F.L.-C.I.O.