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Democratic president candidates Bernie Sanders and Hillary Clinton debate at Saint Anselm College Dec. 19, 2015 in Manchester, New Hampshire. Getty Images

Former Secretary of State Hillary Clinton, Vermont Sen. Bernie Sanders and former Maryland Gov. Martin O’Malley are to face-off Sunday night in the fourth Democratic debate. The debate is scheduled to take place in Charleston, South Carolina at the Gaillard Center, just down the street from the historic Emanuel AME Church.

The debate is expected to be moderated by NBC’s evening news anchor Lester Holt, Politico reported, and candidates will likely discuss topics like guns, inequality and national security, similar to previous debates. Fast-food workers fighting for a $15 an hour minimum wage plan are expected to protest Sunday’s debate, and thousands have planned to gather outside, USA Today reported. Among the candidates, Clinton has said she supports a $12 an hour pay floor while Sanders and O’Malley have both said they back a $15 minimum.

Prior to Sunday night’s debate, a recently released survey from Bloomberg Politics/Des Moines Register revealed Clinton with 42 percent support and Sanders with 40 percent support among likely caucus-goers in Iowa just weeks before the Feb. 1 contests. Ahead of New Hampshire’s primary Feb. 9, a Marist/Wall Street Journal/NBC News poll released a week ago indicated Sanders leads Clinton by 14 percentage points in the state. O’Malley barely qualified for Sunday’s debate and accused the NBC of treating the selection process like “The Apprentice.” Sanders and Clinton both supported O’Malley's inclusion in the debate.

2016 Democratic Primary Debate Schedule | InsideGov

Coverage is to begin online at 8 p.m. EST, and can be streamed on NBCNews.com as well as YouTube.com/NBCNews.com. The debate is scheduled to start at 9 p.m. EST.

After Sunday night’s debate, the next Democratic debate is scheduled for Feb. 11 at the University of Wisconsin-Milwaukee. The next Republican debate is scheduled for Jan. 28 in Des Moines, Iowa, just three days before caucuses.