Steyer has poured millions of dollars into the Palmetto State, flooding the airwaves and building out a large statewide operation. But Steyer, appearing on “Fox News Sunday,“ pointed to his message and the fact that he is "very willing to talk about race" for his increase of support.

"I think I have done best with black people. I have done best with Latinos. I think that when we get to the diverse Democratic electorate, when we get to the diversity that is America and the Democratic Party, I do a lot better," Steyer told host Chris Wallace.

"South Carolina happens to be a place that has a pretty high concentration of African Americans. And those happen to be people that I talked to a lot and have a lot of — a long history of working with, and, therefore, that's a population where I do really well," Steyer added.

Saturday’s South Carolina primary is crucial for Biden's campaign, after fourth- and fifth-place finishes in Iowa and New Hampshire, respectively. The former president did, however, register a second-place finish in Nevada on Saturday with strong turnout among African Americans.

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But as Biden heads into the Feb. 29 primary, potential cracks in his support in the state have emerged.

A Winthrop University poll released last week showed Biden holding a narrow lead over Sen. Bernie Sanders in the state. In the poll, Biden earned 24 percent support, followed by 19 percent support for Sanders and 15 percent for Steyer.

Biden, however, said he remained confident heading into the South Carolina primary.

"I feel good about where we are. I feel good about going into South Carolina," Biden said. "And I feel good about the kind of support I've had with African Americans around the country."