Ben Jealous, the former head of the NAACP, will endorse Bernie Sanders, a source familiar with the campaign told CNN.
The endorsement is a potential boost to Sanders who has struggled to gain traction among African-American voters, though he has made small gains on Democratic presidential rival Hillary Clinton, according to recent polls.
Jealous, 43, is set to appear with Sanders in New Hampshire ahead of the February 9 primary to announce his support.
Elected to the NAACP post in 2008, Jealous was the youngest person to head the civil rights organization. Credited with re-invigorating the organization and making it more politically relevant, Jealous served for four years.
Jealous joins a list of prominent African-Americans who have endorsed Sanders, among them Nina Turner, a former Ohio state legislator, Rep. Keith Ellison and Cornel West.
In South Carolina, a number of state legislators have also endorsed Sanders, including Justin Bamberg who switched his allegiance from Clinton to Sanders.
The most recent poll shows Sanders struggling to attract a sizable number of black voters in South Carolina — Sanders earns 17% of black voters, with Clinton earning 74%, according to a NBC/Wall Street Journal Marist poll.