“Flames seem to be licking through the cracks in Biden’s firewall,” Scott Huffmon, the director of the Winthrop poll, said in a statement. “His support has dropped by double digits since the late September Winthrop Poll.”

In the poll last September, Biden was at 37 percent, 20 points ahead of Warren, the second-place candidate.

Mike Bloomberg was not included in the poll because he is not on the ballot in the state.

The poll, which entered the field one day before the New Hampshire primary and concluded on Wednesday, shows a plurality of black voters still supporting Biden.

Among black voters, 31 percent support the former vice president, to 18 percent for Steyer and 17 percent for Steyer.

A majority of all voters said they have already made up their mind for who to vote for: 55 percent said they’re “very sure” about who they’re voting for, and 43 percent said they might change their mind.

The poll is also an important one for Steyer, who failed to qualify for Wednesday night’s debate in Nevada and hopes to return to the debate stage next week in South Carolina. To qualify for Tuesday’s debate, candidates need to hit 10 percent in four polls approved by the Democratic National Committee (or 12 percent in two South Carolina polls), or win a delegate to the national convention out of the three preceding contests in Iowa, New Hampshire and Nevada.

Steyer’s 15 percent in the Winthrop poll — an approved pollster — gets him halfway to meeting the South Carolina-specific polling threshold. Polls must be released by 11:59 p.m. on Monday to count. Heather Hargreaves, Steyer’s campaign manager, told POLITICO earlier this week that they were confident Steyer would win a delegate in Saturday's Nevada caucuses, which would also put the billionaire on stage.

All six of the candidates who participated in Wednesday night's debate — Biden, Bloomberg, Buttigieg, Klobuchar, Sanders and Warren — have already qualified for the Feb. 25, according to POLITICO's tracking of public polling and delegate estimates.

The Winthrop University poll surveyed 443 likely Democratic primary voters from Feb. 9-19. Results have a margin of error of +/- 4.7 percentage points, and results among black respondents have a margin of error of +/- 5.9 percentage point margin of error.