After poor showings in Iowa and New Hampshire, Joe Biden’s campaign is pinning its hopes on South Carolina — in particular, the black vote there. The rise of Sen. Bernie Sanders and former New York Mayor Michael Bloomberg in the polls has corresponded with a Biden decline, but South Carolina will be the first state to vote where most of the electorate is black, and black voters have disproportionately supported the former vice president for most of the campaign (before people actually started to vote).

So two questions: How well is Biden holding up among black voters in the wake of the first two contests? And how much could the debate on Wednesday night in Las Vegas, which seemed to go poorly for Bloomberg, shift the race in the last few days before Nevada and South Carolina vote?

Two answers: Not particularly well. And maybe quite a bit.

In an average of national polls, Biden’s support among black voters has dropped about 12 percentage points from before the Iowa caucuses to the post-New Hampshire period. Conversely, during the same period, Bloomberg and Sanders (the two other candidates averaging double-digit support among black voters in recent national polls) each gained 10 points among black voters. And recent polls show Biden dropping fast among all voters while Sanders and Bloomberg are gaining ground. So if the Nevada debate really hurt Bloomberg, Biden stands a decent chance of winning back a lot of voters. Not only are he and Bloomberg both running in the same “moderate” lane, but it appears that a lot of voters left Biden for Bloomberg after Iowa and New Hampshire.

Biden’s 12-point drop among black voters is particularly bad considering how much his nomination hopes rest on support from that voting bloc. Black voters account for about one-fifth of the national Democratic primary electorate but make up a disproportionately large share of Biden’s potential electoral coalition — about a third, most likely. Indeed, Biden has dropped 10 points in our national polling average since the Iowa caucuses — from being the national polling leader to finding himself behind Sanders and in a battle with Bloomberg for second — and roughly a quarter of that slide is likely due to his drop among black voters specifically. Proportionally, Biden has actually lost more white support than black support, but he still lost around one-fourth of his support among black voters nationally since Iowa voted.

Biden’s diminished support among black voters matters in Nevada too, where Biden is currently running second to Sanders by about 12 percentage points in our polling average of all the state’s voters. Nevada is more racially and ethnically diverse than Iowa or New Hampshire, and while Hispanic voters form the state’s largest nonwhite voting group, there are a fair number of black voters in the Silver State, too — 13 percent of the 2016 caucus electorate was black, according to the 2016 entrance poll.

But Biden’s standing among black voters matters especially in South Carolina, where 61 percent of Democratic primary voters were black in 2016. Often referred to as a “firewall” for the Biden campaign, the former vice president basically has to win South Carolina — maybe even “win big” — or his campaign could find itself on its last legs.

Indeed, some recent South Carolina polls, though not all, have shown a similar trend to the national polls. Right before Iowa, East Carolina University found Biden leading with 37 percent overall, including 44 percent support among black voters. But in ECU’s latest poll, conducted after New Hampshire, Biden slipped to 28 percent overall (still leading), with 36 percent support among African American primary voters. Another South Carolina survey from The Welcome Party/Change Research dropped on Wednesday, and it found Biden tied for first overall with Sanders at 23 percent, and Biden leading among black voters with 33 percent. Unlike the ECU polls, this wasn’t much of a change for Biden compared to Change Research’s previous South Carolina survey just before Iowa that found Biden at 25 percent overall — 5 points ahead of Sanders — and at 30 percent support among black voters. Meanwhile, another new poll from UMass Lowell found that even if Biden’s black support holds up in South Carolina, it might not be enough to get him the big win his campaign is hoping for — the survey found him ahead of Sanders by just 2 points overall even though 43 percent of black voters backed Biden, double Sanders’s 20 percent support.

Biden doesn’t have to worry about Bloomberg in South Carolina because Bloomberg is not on the ballot there, but there’s another billionaire who may be hurting Biden’s chances of consolidating support among black voters in the Palmetto State: Tom Steyer. The post-New Hampshire polls from ECU, Change Research and UMass Lowell put Steyer at 17 percent, 31 percent and 19 percent among black voters. Indeed, Steyer’s place in the South Carolina race is somewhat analogous to the way Bloomberg may be complicating Biden’s ability to retain support among black voters in Super Tuesday states with sizable African American electorates, as recent polls of North Carolina and Virginia have suggested.

There are reasons to think much of Bloomberg’s rise in the polls among black voters came specifically at Biden’s expense. A large share of both candidates’ support comes from voters who describe themselves as more moderate, a group that includes many black voters. Of course, it’s hard to say how much Bloomberg’s gains are about Biden’s poor performances and how much they’re about Bloomberg’s campaign successfully cutting into Biden’s support — both likely play a role. But Bloomberg is pushing hard for black support among both rank-and-file voters and party elites. He’s holding events with African American groups and spending millions of dollars on advertising, which could help win over older black voters, a demographic group that watches a lot of television. Since Iowa voted, Bloomberg has received more elite backing than Biden, according to FiveThirtyEight’s endorsement tracker, with nine black endorsers backing Bloomberg compared to three for Biden. This includes multiple black members of Congress and mayors in big Super Tuesday states (Houston and Charlotte, North Carolina). This movement toward Bloomberg could reflect some of the changes we’re seeing among black voters at large.

Sanders’s gains, meanwhile, likely have less to do with Biden’s struggles. Instead, Sanders’s uptick in African American support is likely spurred by his early wins in the primary. Sanders started the campaign with essentially a tie in Iowa and a narrow win in New Hampshire. So his positive performances are helping him capture new supporters from lots of demographic groups. Sanders may also have benefited at the margins from the departure of tech entrepreneur Andrew Yang, who had a modicum of black support and whose supporters were far more likely to pick Sanders as their second choice than any other candidate. Unlike Bloomberg, Sanders doesn’t have any recent endorsements from black leaders in our tracker, but that certainly hasn’t stopped him from winning over some African American voters.

Now the question is whether Biden can maintain enough support among black voters to get a win in South Carolina. The fact Steyer failed to make the Nevada debate could help the former vice president there, and more broadly any erosion in Bloomberg’s support in the wake of the debate could help Biden win back black voters across the country. And a Biden victory in South Carolina might produce a “comeback” narrative that could dramatically shift the tone of media coverage surrounding Biden’s campaign and help him remain competitive in the larger nomination race.

If Biden’s falling support is mostly about his poor performances in the first couple states, a respectable showing in Nevada and a win in South Carolina could turn things around. And if Biden’s slide has as much or even more to do with Bloomberg’s overwhelming advertising firepower and his effort to win over black elites and voters, the former vice president might not be able to recover even if he has a solid performance in South Carolina later this month — unless, of course, the Wednesday night debate really cuts into Bloomberg’s standing. Regardless, Biden’s current trajectory among black voters is a serious problem for his campaign, so he absolutely needs something to change for the better.