Former Vice President Joe Biden Joe BidenMomentum growing among Republicans for Supreme Court vote before Election Day Trump expects to nominate woman to replace Ginsburg next week Video of Lindsey Graham arguing against nominating a Supreme Court justice in an election year goes viral MORE's lead in South Carolina continues to narrow as the state's primary inches closer, according to a new CBS News-YouGov survey.

The poll, which was finished before Sen. Bernie Sanders Bernie SandersNYT editorial board remembers Ginsburg: She 'will forever have two legacies' Two GOP governors urge Republicans to hold off on Supreme Court nominee Sanders knocks McConnell: He's going against Ginsburg's 'dying wishes' MORE (I-Vt.) won the Nevada caucuses, revealed that Biden's support has fallen by double-digits and that he leads the progressive senator by just 5 points. Biden, who once led the field by nearly 30 points, earned 28 percent support among Democratic voters and independents who plan to vote in the primary.

Twenty-three percent of respondents said that they would place their support behind Sanders. Billionaire activist Tom Steyer Tom SteyerTV ads favored Biden 2-1 in past month Inslee calls Biden climate plan 'perfect for the moment' OVERNIGHT ENERGY: Trump administration finalizes plan to open up Alaska wildlife refuge to drilling | California finalizes fuel efficiency deal with five automakers, undercutting Trump | Democrats use vulnerable GOP senators to get rare win on environment MORE came in third, with 18 percent of respondents saying they favored him as the nominee.

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Meanwhile, 12 percent of respondents said they favored Sen. Elizabeth Warren Elizabeth WarrenBiden's fiscal program: What is the likely market impact? Warren, Schumer introduce plan for next president to cancel ,000 in student debt The Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon MORE (D-Mass.), while 10 percent said they would back former South Bend, Ind., Mayor Pete Buttigieg Pete ButtigiegBipartisan praise pours in after Ginsburg's death Bogeymen of the far left deserve a place in any Biden administration Overnight Defense: Woodward book causes new firestorm | Book says Trump lashed out at generals, told Woodward about secret weapons system | US withdrawing thousands of troops from Iraq MORE. Just 4 percent of voters said they supported Sen. Amy Klobuchar Amy KlobucharThe Hill's Morning Report - Sponsored by The Air Line Pilots Association - White House moves closer to Pelosi on virus relief bill EPA delivers win for ethanol industry angered by waivers to refiners It's time for newspapers to stop endorsing presidential candidates MORE (D-Minn.).

Former New York City mayor Michael Bloomberg Michael BloombergTop Democratic super PAC launches Florida ad blitz after Bloomberg donation The Hill's 12:30 Report - Presented by Facebook - Latest with the COVID-19 relief bill negotiations The Memo: 2020 is all about winning Florida MORE (D) is not competing in South Carolina, instead focusing his campaign on Super Tuesday states.

Despite poor showings in Iowa and New Hampshire, Biden's campaign has continued to express confidence about his standing in the field, claiming that diverse states such as South Carolina will propel his candidacy. He finished in second place in Nevada, the first state to hold a nominating contest that is not overwhelmingly white, but the latest survey shows that his support has fallen significantly among African Americans in South Carolina.

Biden still leads in that category with 35 percent support, though the figure represent a 19-point decline since November. Steyer, who had just 2 percent support among that bloc last fall, now has 24 percent support. Sanders is close behind with 23 percent support among African Americans, which make up a majority of the Democratic electorate in South Carolina.

Biden on Sunday attributed his decline in support among African Americans to Steyer's campaign, saying, "I think a lot’s happening in terms of the amount of money being spent by billionaires to try to cut into the African American vote."

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The CBS-YouGov survey also found that three in 10 voters who supported Biden in November have switched their support, with about half of those now backing Steyer.

Sanders further cemented his status at the frontrunner to be the Democratic nominee with a decisive victory at the Nevada caucuses on Saturday. The win comes on the heels of a win in New Hampshire and as polls show him far outpacing his competitors.

The CBS-YouGov survey was conducted among a sample of 2,000 registered South Carolina voters between Feb. 20 and Feb. 22. It has margin of error of 5.5 percentage points.