Democratic presidential candidate Bernie Sanders and his wife, Jane O'Meara Sanders, take the stage during a rally at Bon Secours Wellness Arena in Greenville, S.C., on Feb. 21. (Cassi Alexandra for The Washington Post)

GREENVILLE, S.C. -- At a Bernie Sanders rally here Sunday night, the Democratic presidential hopeful was introduced to a crowd of more than 5,200 people by a pair of high-profile African American supporters: actor Danny Glover and former NAACP leader Benjamin Jealous.

It was the first rally that Sanders has held in South Carolina since his loss to Hillary Clinton in Saturday’s Nevada caucuses, where entrance polls showed Clinton winning black voters by an overwhelming margin.

African Americans will be key to the fate of the candidates in South Carolina on Saturday, when black voters are expected to account for more than half of the Democratic primary electorate. Sanders’s ability to connect with African Americans remains a challenge for his campaign, as evidenced by Sunday's crowd, which was very white.

In a joint interview backstage at Sanders’s event here, Jealous and Glover talked about why they are backing the senator from Vermont and his prospects for winning over more African American voters in South Carolina and elsewhere with his message of economic fairness.

“I think the easy part of getting black voters to turn to Bernie Sanders is what happens when they actually listen to him,” said Jealous, who served as president and chief executive of the NAACP from 2008 to 2013. “The hard part is getting beyond the Clinton brand. The Clinton brand is a bit like Coca-Cola. You know, it’s a Southern brand. Everybody knows it. It tastes good. The question you have to ask is: Is it the best option for you?”

Asked if there’s enough time for Sanders to make the kind of conversions he needs to be competitive, Jealous said that remains an open question.

“What is certain is Clinton has hit her high-water mark in the black community,” he said. “The question is how far her support will fall [and] how fast. Right now, a lot of people in South Carolina still haven’t made up their minds.”

Jealous said the process of African American voters moving to Sanders reminded him of what happened when Barack Obama ran for president in 2008.

“It’s younger people turning on older people,” said Jealous, 43, who was the NAACP’s youngest leader in its history. “It’s common to talk to mothers who have turned to Bernie because their daughters turned them on to the campaign.”

Glover, 69, may be best known for his roles in the “Lethal Weapon” movies with Mel Gibson, but he has a long history of activism on civil rights and labor issues dating to the late 1960s.

“I think that African American voters are astute and certainly intelligent enough to see the difference, and I think they’re beginning to see the difference,” Glover said when asked about the status of Sanders’s race against Clinton. “You know, most of what you’ve heard before is people saying, ‘We don’t know who Bernie Sanders is.’ Once you begin to hear what he’s about -- and that’s the responsibility of all of us as citizens -- that changes. The responsibility that I see as an artist is simply to be a truth sayer and to say what I see.”

Glover said he met Sanders only in the past week. The actor said he reached out to Sanders’s campaign asking what he could do to help.

“To find someone like Bernie Sanders, someone who has integrity, who believes in our role as ordinary citizens who are able to place demands on governance -- I came on board on the basis of that,” Glover said. “I wasn’t asked to come on board. … I saw this opportunity.”

Both Glover and Jealous have cut social media and television ads for Sanders. And both plan to campaign with him and serve as surrogates in the months to come.

Jealous said he has been traveling to “the blacker parts” of South Carolina to campaign for Sanders, characterizing Greenville, the site of the rally, as “the whitest corner of the state.”

Jealous, who lives in Maryland, said he waited to endorse Sanders until former Maryland governor Martin O’Malley dropped out of the presidential race. As head the NAACP, which is based in Baltimore, Jealous worked with O’Malley on several issues, including Maryland’s abolishment of the death penalty in 2013.

Jealous said he met Sanders during his tenure as NAACP president.

“He was one of those senators we could always count on,” Jealous said. “I wish I had spent more time with him, but frankly I spent more time with folks who we were worried about doing the wrong thing. That’s just the nature of lobbying.”

Given Sanders’s record, both as a member of Congress and as a civil rights activist from his days as a college student in the 1960s -- Jealous said he has been distressed by efforts from the Clinton campaign to question Sanders’s commitment to the cause.

“The reality is the Clinton campaign is following the Karl Rove playbook, trying to attack Bernie where he’s strongest,” Jealous said, referring to the well-known strategist for former president George W. Bush.

Sanders, Jealous said, is “the only true 1960s-movement person running for president.”

“Danny and I are both movement people, and the difference for us between this campaign and the other campaign is this isn’t just a campaign the references our movement or respects our movement,” Jealous added. “It’s really an extension of the same movement that we come out of.”