Volunteer Jada Williams, a 20-year-old junior at the University of South Carolina, goes door to door canvassing for votes for Hillary Clinton on Sunday. (Vanessa Williams/The Washington Post)

As Jada Williams worked a middle-class, mostly black neighborhood here ahead of primary day — clipboard and Hillary Clinton door-hangers in hand — she was not surprised to see brochures for Bernie Sanders tucked into the same storm doors she was targeting.

Out from one walked Sonya Penager, who pronounced herself a Clinton backer. “She has 40-plus years of experience, and she has a husband who was president. And I liked her husband when he was president,” Penager, 50, said.

Did she consider voting for Sanders? “No,” Penager said with a shrug.

Penager echoed many other African Americans here, who have largely proved to be immune to the passion and idealism that has motivated so many others to feel the Bern. Like Penager, most black voters in South Carolina do not appear to be giving Sanders much of a chance — most say they don’t know what he’s done during his three decades in Congress or what he stands for, and those who do are highly skeptical any of it will ever come to be.

But African Americans here know Clinton well and, while more fond of than in love with her, they appreciate her real-world message of what can and can’t be accomplished in Washington. Many also retain good memories of Bill Clinton’s presidency and especially like that Hillary Clinton has promised to continue President Obama’s policies.

Across the South, candidates are battling for the young black vote with the hope of carrying this important Democratic constituency. Growing support for Bernie Sanders has left many older voters, who favor Hillary Clinton, questioning the political judgement of the younger generation. (Dalton Bennett/The Washington Post)

Clinton’s strong support among African Americans is proving to be the decisive factor in the Democratic primary. In the first three states to vote — Iowa, New Hampshire and Nevada — entrance and exit polls showed Sanders about even or ahead of the former secretary of state among white voters. An entrance poll of the Nevada caucuses showed Sanders winning Hispanic voters as well, though the Clinton campaign has disputed whether that is accurate.

Nonetheless, Clinton’s five-percentage-point win was propelled in large part by her support among black voters, who comprised 13 percent of the electorate and gave Clinton 76 percent of their support. Polls here and across many of the Southern states that vote on Super Tuesday next week show a similar spread.

An NBC News/Wall Street Journal/Marist poll released Feb. 19 showed Clinton getting 68 percent of support among black voters to 21 percent for Sanders. The split was 78 percent to 12 percent in Clinton’s favor among African Americans older than 45. Among white voters, Sanders had a slight lead of 51 percent to 46 percent, leaving Clinton ahead overall by nearly 30 points.

Sanders, in an interview this week with The Washington Post, said his strong showing among Latino voters in Nevada suggests he can challenge her for black voters as well.

“I know the Clinton people were very nervous when there was an [entrance poll] in Nevada that we won the Latino vote,” Sanders said. “We have made good progress in the Latino community, we are making good progress in the African American community, but I will not deny to you that we still have a way to go, and what we have got to do is a better job in getting our record out and talking about the issues, which are creating decent-paying jobs and reforming a broken criminal-justice system, which has been very, very harsh on the African American community.”

That message is resonating to a degree here, particularly among younger voters who dislike the Clintons for pushing the 1994 crime bill that led to harsher penalties and an explosion in the incarceration rate for African Americans and Hispanics.

Sanders’s racial justice platform, which calls for reducing the high incarceration and unemployment rates for communities of color “speaks to me as a young African American male,” said Hamilton Grant, 27, co-chair of South Carolina Young Leaders for Bernie.

Bernice Scott, a political activist and Hillary Clinton supporter, prays next to Kevin Washington Jr., 17, at her Baptist church just outside of Columbia, S.C. (Melina Mara/The Washington Post)

Grant is having a tough go of convincing others — even in his own family. “I think my brother is leaning toward Bernie,” he said. “My sisters are on the fence, but I think they may pick Hillary.”

Jeff Weaver, Sanders’s campaign manager, acknowledged that the campaign faces a tough test on Saturday but said Sanders has no plans to concede the first primary in the South to Clinton.

“We are certainly going to be down there to compete, but we’re going to have to appear in a host of other states as well,” he said, alluding to the 11 states that have primaries or caucuses just a few days later on Tuesday. Some of those states, including Minnesota, Massachusetts and Sanders’s home state of Vermont, are outside of the South and have smaller African American populations.

Clinton has more aggressively challenged Sanders’s proposals as unrealistic in recent weeks, and on Monday at a campaign even in Sumter, he pushed back, saying his ideas are not radical and warning against accepting an incremental approach to public policy. “If we had that mentality of thinking small, do you think we would have had an African American as president of the United States today?”

On Wednesday, Sanders went after Clinton’s support, as first lady, for a welfare reform bill in the 1990s that other progressives have criticized as having exacerbated an already disproportionate poverty rate among black women.

“What welfare reform did, in my view, was to go after some of the weakest and most vulnerable people in this country,” Sanders said at a news conference in Columbia, noting that he voted against the bill.

Sanders has built a campaign operation in South Carolina, paying dozens of canvassers $15 an hour to campaign door-to-door, and he has scored a few high-profile endorsements, including the popular former NAACP leader Benjamin Jealous. On Tuesday, movie director Spike Lee endorsed “my brother, Bernie Sanders,” urging voters to “wake up!”

Sanders is advertising on radio and television and, unlike an early ad that drew criticism because it showed almost no people of color, people of all races and ethnicities are featured in the spots running in South Carolina.

Still, he has struggled to attract a large following among African Americans with his socialist pitch.

“Democratic socialism does not work,” said Norman Jackson, 60, a Richland County commissioner, who was part of a group of people that gathered to talk about the campaign Saturday at St. John Baptist Church in Hopkins, a small town about 25 minutes south of Columbia. “There’s no such thing as free [college] education for everyone; someone has to pay for it.”

Williams, the Clinton volunteer, said she considered Sanders but ultimately felt like he was promising more than he could deliver.

“His ideas sound good when he’s saying them,” said Williams, a 20-year-old junior at the University of South Carolina, “but when you really think about it and ask yourself, will this actually be accomplished, it’s a lot more fantastical, as opposed to Secretary Clinton, whose ideas are much more realistic.”

John Wagner contributed to this report.