Joe Biden leaving a campaign event in Georgetown, South Carolina on Feb. 26, 2020. Tucker Higgins / CNBC

GEORGETOWN, S.C. — Joe Biden was on a roll. Feeding off the buzzing energy on the second floor of an event venue in this tiny town north of Charleston, the former vice president detailed his plans for health care, education and even for dredging the local port. At long last, about an hour into Biden's remarks, state Rep. Carl Anderson interjected. "He reminds me of a preacher, when he gets going and he leans back. And everyone says, 'He said one more minute!'" Anderson said. There are worse things, for a Democrat in the South, than getting compared to a preacher. Biden joked that Anderson, a local supporter, was trying to get him to shut up. But he relented. He asked for some questions he could answer yes or no. Then a supporter asked if he was going to win. "Yes!" Biden said, as the crowd erupted around him. "South Carolina is the trajectory to winning the Democratic nomination!" The applause was the biggest of the day.

Biden's biggest moment yet

Biden had been considered the front-runner for the Democratic nomination before he stumbled to fourth place in the Iowa caucuses and fifth place in the New Hampshire primary earlier this month. After a second-place finish in the Nevada caucuses last week, though, he is experiencing surging momentum in this Southern state, which he has called his "firewall." Just a week ago, his lead over Sen. Bernie Sanders, I-Vt., in polling averages was as tight as 2%. Now the gap is in the double digits. And that difference was already widening when, on Wednesday, Biden secured the endorsement of South Carolina's most powerful Democrat, Rep. James Clyburn, the House majority whip. South Carolina's Democratic presidential primary on Saturday will be the most important event of the Biden candidacy to date. The Biden campaign, which spent the first months of the race coasting with front-runner status before taking a beating when voting started in the early states this month, has pegged its own viability to a strong showing among Democrats here. Biden himself predicted a win during the Democratic debate in Charleston this week. Public polling and interviews with Democrats around the state suggest that Biden will do well. In particular, Biden is expected to outperform among black voters, especially those who are older or religious. Black voters especially describe Biden as a known quantity, a candidate they have known and liked since his days with former President Barack Obama, or even earlier. "The name that's known in the community is Biden," said the Rev. Andrew Adams, whose church is located in North Santee, an unincorporated territory in Georgetown County. "I've talked to a lot of people about Bernie," Adams said of Sanders, who has become the front-runner in the race for the nomination. "They don't understand 'Medicare for All,' that situation. He's not answering questions. He's vague about how he's going to make it happen. They are a little suspect about that, so I think that's a turnoff."

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