Vermont Sen. Bernie Sanders lunched with the rapper Killer Mike, visited the Martin Luther King Jr. Center and urged a crowd of more than 4,000 at the Fox Theatre on Monday to "keep his extraordinary vision alive" as he tried to boost his black support in the South.

The presidential contender lags far behind Democratic front-runner Hillary Clinton in polls of black voters, who make up the brunt of the party's electorate across the region. Her campaign is counting on a Southern firewall to stop Sanders in case he wins the early contests in Iowa and New Hampshire.

“He kept his eyes on the prize,” Sanders said of King. “Victory does not come easily. Struggle does not come easily. And what we need to do is to keep our eyes on the prize. Always, always fighting for what he called the beloved community.”

He added, to cheers from the crowd: “Real change always takes place from the bottom on up. Never from the top down.”

Sanders visited Atlanta and Savannah as part of a Southern swing that also brought him to South Carolina over the weekend. Earlier Monday, the 74-year-old met privately with Bernice King, one of the slain civil rights leader's children, to talk about her father's legacy.

Killer Mike – his real name is Michael Render – got roars of applause when he warned against a return to Reagan-era policies and inveighed against Clinton, calling her “a new Margaret Thatcher."

Sanders opened his speech with a lengthy tribute to King's legacy before accusing Republican presidential candidates of using "racist and outrageous attacks" about outsiders.

'"They are trying to open the door to racism, whether it’s against our Hispanic brothers and sisters or Muslims," said Sanders. "And we are going to shut that down."

The crowd, he said, is sending a message to the billionaires: "You cannot have it all. You're not going to get huge tax breaks when children in Georgia and Vermont go hungry."

He also touted a criminal justice reform proposal that would seek to change mandatory minimum sentences, decriminalize  and bolster prison rehabilitation programs.

"We will have our young people at work and in school," he said, "not rotting behind jail cells."

And he gave the Democratic partisans in the crowd more red meat when he blasted income inequality, promised to give new mothers 12 weeks of paid family leave and reduce what he called barriers to voting, such as the voter ID laws that have swept many Republican states in the region.

"When you do that you’re nothing less than a political coward," he said of efforts to "suppress the vote." "And if you are too afraid to run in a free and fair election, get another job"

Several of the thousands at the Fox Theatre expressed a barely-concealed contempt for Clinton - though they each said they would hold their nose and vote for her should she defeat Sanders.

“Bernie is the only one I feel is working for us instead of the donors. We are his donors,” said Dan DeYoung, a 65-year-old retired electrician among the Sanders groupies awaiting his arrival. “I’ll vote for Hillary – but only barely. I’ve said all along that I don’t trust her. But if she’s the Democrat, how can I go with republicans. They are so silly.”

Nick Selby, a Georgia Tech student who waited with two friends outside for Sanders’ arrival, canvassed for Barack Obama in 2012 but he’s not nearly as thrilled with Clinton’s campaign this year. He hardly hesitated when asked why he supported the Vermont senator over Clinton.

“My biggest issue is campaign finance reform. There are plenty of other issues, but they can’t get accomplished until we solve campaign finance reform,” said Selby, adding: “I don’t think Hillary will be able to get young voters super excited. It’s hard to defend someone with her record.”

Keith Bussey, a 54-year-old small business owner, was one of a smaller group of black supporters in the audience. Sanders has an uphill battle, Bussey said, but he has better stances than his opponent on college affordability, healthcare and criminal justice reform.

"My wife supported Hillary - until she started to listen to both candidates. Now she's feeling the Bern," said Bussey. "I think people will start coming over. They just need to listen to him."