Joe Biden had a disappointing showing in the first three contests of the Democratic primaries, but the former vice president expressed confidence Tuesday night after the South Carolina debate that he will win the state's primary. Biden spoke with CBS News' Major Garrett in the spin room after the explosive debate, hosted by CBS News and the Congressional Black Caucus Institute.

"I'm going to win South Carolina," Biden said. He said that his margin of victory didn't matter, just that he succeeded.

"I think it's just important that I win. One point is enough, but I think I'm going to win by a lot more than that," Biden said.

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At one point in the fall, Biden had a 28-point lead in South Carolina, but it has shrunk to a slim single-digit lead, according to the CBS News Battleground Tracker on February 23. Sanders, who won in New Hampshire and Nevada and topped in the popular vote in Iowa, trailed Biden by only 5 points in that poll, with 23% of the vote compared to Biden's 28%.

South Carolina has a large black population, and Biden repeated that he had "earned" the African American vote.

"The African American community knows me, my record. They've known me for the last 40 years," Biden said, adding that he wasn't "Johnny come lately" to civil rights issues.

Biden also said that he believed the first two primaries in Iowa and New Hampshire, two states with a majority white population, did not reflect the diversity of the country. He touted his support among black voters.

"No Democrat has ever won without overwhelming black support. It's not possible to win," Biden said.

Biden, in particular, attacked Tom Steyer, who has been creeping in the polls in South Carolina after investing a significant amount of time and money in the state, during the debate. According to the CBS News Battleground Tracker on February 23, Steyer has rocketed to third place in the state with 18%.

Biden referred to Steyer as a "Tommy come lately" while hitting him on his record on private prisons.