Former Vice President Joe Biden Joe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE has a 20-point lead against the rest of the 2020 Democratic field in the crucial early primary state of South Carolina as the Palmetto State emerges as a firewall for his campaign.

Biden has the support of 37 percent of Democratic or Democratic-leaning registered voters surveyed, while Sen. Elizabeth Warren Elizabeth WarrenOvernight Defense: Appeals court revives House lawsuit against military funding for border wall | Dems push for limits on transferring military gear to police | Lawmakers ask for IG probe into Pentagon's use of COVID-19 funds On The Money: Half of states deplete funds for Trump's 0 unemployment expansion | EU appealing ruling in Apple tax case | House Democrats include more aid for airlines in coronavirus package Warren, Khanna request IG investigation into Pentagon's use of coronavirus funds MORE (D-Mass.) got 17 percent in a new Winthrop University poll released Tuesday.

Sens. Bernie Sanders Bernie SandersSirota reacts to report of harassment, doxing by Harris supporters Republicans not immune to the malady that hobbled Democrats The Hill's Morning Report - Sponsored by Facebook - Republicans lawmakers rebuke Trump on election MORE (I-Vt.) and Kamala Harris Kamala HarrisTexas Democratic official urges Biden to visit state: 'I thought he had his own plane' The Hill's Campaign Report: Biden on Trump: 'He'll leave' l GOP laywers brush off Trump's election remarks l Obama's endorsements A game theorist's advice to President Trump on filling the Supreme Court seat MORE (D-Calif.) and South Bend, Ind., Mayor Pete Buttigieg Pete ButtigiegBillionaire who donated to Trump in 2016 donates to Biden The Hill's Morning Report - Sponsored by Facebook - GOP closes ranks to fill SCOTUS vacancy by November Buttigieg stands in as Pence for Harris's debate practice MORE rounded out the top five with 8 percent, 7 percent and 4 percent, respectively.

ADVERTISEMENT

No other candidate scored above 3 percent.

Biden’s lead swelled to 37 points among African American registered voters who identified as Democratic or leaning Democratic, winning 46 percent of those respondents.

Harris came the closest to Biden, with 10 percent, while no other candidate broke single digits. White voters who identified as Democratic or leaning Democratic said they prefer Warren to Biden by a 29 percent to 22 percent margin.

But the poll showed signs the electorate could shift, as only a third of those surveyed said they were sure of their choice and 52 percent said they might change their minds.

South Carolina will hold the 2020 cycle’s fourth nominating contest after Iowa, New Hampshire and Nevada and will represent the first time the crowded primary field is judged by a majority-black primary electorate.

“African Americans constitute one of the most important constituencies for the Democratic Party. African Americans can make up more than 60% of the Democratic Presidential Primary vote in South Carolina, which is a much larger portion than in the Iowa Caucus or New Hampshire primary,” said Winthrop Poll Director Scott Huffmon.

The Winthrop University poll comes as Biden fends off a growing challenge from Warren, who has leapfrogged him in a handful of national polls and statewide polls in Iowa and New Hampshire.

The former vice president still enjoys a deep well of support among African American voters over his time in the Obama administration, with his campaign hoping the demographic can help deliver Biden a victory in South Carolina’s primary and propel him to the Democratic presidential nomination.

The Winthrop University poll surveyed 462 Democratic and Democratic-leaning registered voters from Sept. 21-30 and has a margin of error of 4.6 percentage points. The data was weighted based on age, sex and race.