The contest in South Carolina looks very different heading into its final week than it did last fall. Joe Biden (28%) has only a single-digit lead with Bernie Sanders (23%) now right behind him. The race has narrowed considerably since the fall, when Biden led the field by a whopping 28 points. Support for the former vice president has fallen by double-digits as Sanders and businessman Tom Steyer have made gains. Steyer is at 18%.

This poll was finished before Sanders coasted to a win in the Nevada caucuses Saturday night — though most South Carolina voters told us the Nevada results would not impact them.

Although Biden continues to lead among African Americans — who make up a majority of the state's Democratic electorate — his support with black voters has declined 19 points since the fall.

Biden has lost ground with white voters, too. He led with whites in November, but Sanders does now.

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Steyer has shot up into the top tier in this race with 18% of the vote, up from 2% in November. Support for him has risen sharply among black voters.

Among South Carolina Democrats who were recontacted as part of the survey, three in 10 voters who supported Biden in November have switched to another candidate — half of them (15%) now support Steyer.

Defeating President Trump is the top priority for South Carolina Democrats, including both black and white voters, but black voters express more confidence than white voters that the Democrats will nominate someone who can actually do that: 46% are very confident, compared to just 19% of white voters.

Black voters pick Biden as the candidate with the best chance to beat Mr. Trump, while whites are split between Biden and Sanders.

Many black voters feel Biden understands the needs and problems of black voters "a lot" — higher than any other candidate. Steyer and Sanders also do well on this measure. For most of the candidates, a majority of black voters say they understand their concerns, at least some.

Buttigieg has not gained much traction with black voters since the fall, and just 13% say he understands the needs and problems of black voters a great deal — far lower than current frontrunners. Buttigieg is getting 4% of the black vote now, compared to 2% in November. Elizabeth Warren and Amy Klobuchar are also getting single-digit support among black voters.

Biden's performance in the early contests of Iowa and New Hampshire may be hurting him some. Nearly four in 10 South Carolina Democrats (including most white voters) think the results of those two races make it less likely he will be the nominee. Among this group of voters, Sanders is the top choice and the candidate they think has the best chance of defeating Mr. Trump.

In the days leading up to the primary, health care is the top issue South Carolina Democrats want to hear about (42%), followed by the economy and jobs (30%) and gun policy (12%).

This CBS News survey is conducted by YouGov between February 20-22, 2020. A representative sample of 2,000 registered voters in South Carolina was selected, including 1,238 self-identiﬁed Democrats, as well as independents who plan to vote in the Democratic primary this year. This sample was weighted according to gender, age, race and education based upon voter registration lists and the U.S. Census Current Population Survey, as well as the 2016 presidential vote. The margin of error is approximately 5.5 points.

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