Former Vice President Joe Biden only holds a four-point lead over Sen. Bernie Sanders (I-VT) in South Carolina, signaling that his “firewall” in the state could be in trouble, according to a poll released Thursday.

A Post and Courier poll shows Biden with 28 percent of support among likely Democrat voters, with Sanders in a close second with 24 percent. Billionaire and impeachment activist Tom Steyer enjoys 16 percent support, Sen. Elizabeth Warren (D-MA) has 12 percent, while former South Bend, Indiana, Mayor Pete Buttigieg is at 11 percent, the survey said. Biden topped the same poll by a whopping 31 points in May.

The influential South Carolina newspaper’s figures show that Saturday’s primary content could be tighter than expected.

In contrast, the latest Monmouth University poll shows Biden leading by a comfortable 20 points, while a recently Public Policy Polling survey found the former vice president up by 15 points. In one of the more narrower surveys, East Carolina University found Biden is leading his White House rivals by 8 percent.

The Post and Courier poll comes as Steyer, a self-funding longshot candidate, has focused heavily on a strong finish in South Carolina. He’s spent over $22 million on advertising in South Carolina, according to data analysis from CMAG/Kantar Media. “Oh, there’s no question about that,” Rep. Jim Clyburn (D-SC), the highest-ranking black member of Congress and A kingmaker of in the state’s Democrat political orbit, told ABC News when asked if Steyer has chipped away at Biden’s support with black voters. Clyburn endorsed Biden on Wednesday.

South Carolina is largely seen as a “do-or-die” state for Biden to win decisively after poor showings in the Iowa caucuses and New Hampshire primary. Following the Democrat primary debate in Charleston, Biden expressed confidence that he will take the top slot in the state’s primary.

“I’m going to win South Carolina,” the former vice president told CBS News in the spin room.

“I think it’s just important that I win. One point is enough, but I think I’m going to win by a lot more than that,” he added.