The comments underscore the importance of the black vote in subsequent primary states, especially in the upcoming South Carolina contest, where African Americans make up more than half of the electorate. Clinton's campaign has said that they believe she will hold onto her sizable lead with black voters, despite Sanders's outreach efforts.
"It's good to have new friends, I would prefer to have a true friend," Jeffries said. "Hillary Clinton has been a true friend to the African American community for the last 40 years."
Clinton has sharply pivoted to minority voters coming out of New Hampshire where she lost to Sanders by a more than 20-point margin. The campaign announced the endorsement of South Carolina House Democratic Leader J. Todd Rutherford on Wednesday and a slew of other political leaders in the state.
Rutherford joined Jeffries in sharply denouncing Sanders for being "missing in action" on issues that matter to black voters.
Rutherford faulted Sanders for voting in favor of a 1994 Violent Crime Control and Law Enforcement Act, which has been blamed for helping to usher in an era of mass incarceration. Former president Bill Clinton, who signed the bill into law, has expressed regret for the consequences of the legislation.
"He only really started talking about issues concerning African Americans in the last 40 days," Rutherford said. "On the question of social justice for African Americans, the record is thin."
Meanwhile, Sanders met with civil rights leader Al Sharpton in New York City on Wednesday morning to discuss issues of race. And a week ago, Sanders landed the endorsement of former NAACP chairman Ben Jealous.
Another Clinton endorser on the call, Hazel Dukes, a former president of the New York chapter of the NAACP, suggested that Sanders never had to think about issues that concern African Americans because he was an elected official in a state that is "essentially homogeneous."
Dukes discounted the fact that Sanders participated in the March on Washington with thousands of others and Martin Luther King Jr. in the 1960s, and also that as a college student, he was arrested for protesting segregated housing at the University of Chicago.
"He was probably a participant," Dukes said of the March on Washington. "There were many people participating in that march, so what does that mean?"
"I walked in Washington. Thousands of people walked in Washington," she added.