Joe Biden might need to check his firewall.
The former vice president's lead in South Carolina keeps shrinking in Post and Courier-Change Research polls as the 2020 Democratic presidential primary gets closer — and even after a key competitor for Palmetto State votes, U.S. Sen. Kamala Harris of California, dropped out of the race.
The latest poll released Thursday shows Biden with just a 7 percentage point lead among likely voters in the South's first primary, the first time he has not held a double-digit advantage in seven Post and Courier-Change Research surveys taken since February.
Most consider South Carolina a must-win for Biden as he stumbles in Iowa and New Hampshire. Biden led the S.C. race by as much as 31 percentage points in May. Now, challengers are slicing into his dominant lead among African American voters in the first primary state with a significant black population.
Aided by voters under 50, U.S. Sen. Bernie Sanders of Vermont is continuing his recent national surge in South Carolina, where he has supplanted U.S. Sen. Elizabeth Warren of Massachusetts for second place.
Sanders gained the most support of any candidate since the last Post and Courier-Change Research poll taken in October. He added 7 percentage points to pass Warren, whose backing was unchanged.
Sanders' poll numbers have risen in other early voting states since Thanksgiving, where he has become the leader in New Hampshire and the second choice in Iowa, according to data tallied by Real Clear Politics.
In the new South Carolina poll, Biden leads with 27 percent, followed by Sanders at 20 percent and Warren at 19 percent.
They have separated from the next group of challengers led by South Bend, Ind., Mayor Pete Buttigieg, who, despite his success in other early voting states, cannot find strong black support in a state with a large African American voting base.
Buttigieg, who has become the leader in Iowa and the second choice in New Hampshire, has 3 percent of S.C. African American voter backing in the latest poll, roughly his average from previous surveys.
Overall, Buttigieg received 9 percent of S.C. support, followed by U.S. Sen. Cory Booker of New Jersey and billionaire businessman Tom Steyer, both at 5 percent, with Hawaii Congresswoman Tulsi Gabbard at 4 percent.
Steyer has flooded South Carolina with television and online advertisements. Gabbard has billboards across the state.
The latest entrants to the race showed up in the new poll — billionaire businessman Michael Bloomberg got 3 percent, while former Massachusetts Gov. Deval Patrick received 1 percent. Bloomberg does not plan to campaign in early voting states so he can focus efforts on delegate-rich Super Tuesday taking place three days after the South Carolina primary.
The poll was taken after Harris, who had been running fourth in South Carolina, dropped out of the race on Dec. 3.
Harris, one of three African Americans in the race with Booker and Patrick, was the second favorite among S.C. African American women, a top voting bloc in the state's primary. Black voters account for two-thirds of Democratic primary ballots in South Carolina.
Both Biden and Warren gained the largest amount of support from black female voters with Harris' departure, each gaining 11 percentage points. Biden leads 41 percent to Warren's 25 percent among the key faction.
The former vice president leads with all S.C. black voters at 37 percent but his advantage is slipping.
Warren posted strong gains since the October poll to stand second at 25 percent. Sanders is third at 16 percent.
Biden led the S.C. African American vote by 21 percentage points in October and by twice as much in May.
Booker, who is betting on a good showing in South Carolina, gained support overall with African American voters but was unchanged with black women. Patrick got 1 percent of African American voter support.
The poll of 392 likely Democratic primary voters taken Dec. 6-11 has a margin of error of plus or minus 4.9 percent.