When former Vice President Joe Biden proclaimed “I will win South Carolina,” at Tuesday’s Democratic debate in Charleston, it wasn’t just braggadocio — all of the most recent South Carolina polls suggest he’s right.

In fact, nearly every poll taken in February found Biden to have a sizable lead on his fellow candidates.

For instance, in a Monmouth University telephone poll of 454 likely Democratic primary voters taken just ahead of that debate — from February 23 to 25 — Biden had a 20 percentage-point lead on his nearest rival in the state, Sen. Bernie Sanders. (Sanders is still considered the frontrunner in the race nationally.)

Overall, that poll found Biden to have 36 percent support in the state; Sanders nearly tied with entrepreneur Tom Steyer, with 16 and 15 percent support, respectively; Sen. Elizabeth Warren in fourth with 8 percent support; and former South Bend, Indiana, Mayor Pete Buttigieg and Sen. Amy Klobuchar with 6 and 4 percent support, respectively. The only other candidate on the Democratic ballot Saturday, Rep. Tulsi Gabbard, had 1 percent support.

The Monmouth poll does have a 4.6 percentage point margin of error, but that margin is small enough to protect Biden’s lead. It could, however, mean that the race for second is even closer than it appears, with either Steyer, Sanders, or Warren occupying the number two spot.

While a number of other recent polls found similar results — a February 17-25 poll from Clemson University found the former vice president to have an 18 percentage point lead and a February 26-27 Emerson College survey a 16 percentage-point lead — Biden’s lead isn’t quite that strong across the board.

A Post and Courier poll of 543 likely primary voters taken February 23-27, for example, saw Biden only 4 percentage points ahead of Sanders, at 28 percent support to the senator’s 24 (with Steyer and Warren again in third and fourth). Unlike the Monmouth results, Biden’s lead in this poll is within its 5.1 percentage point margin of error.

All these polls suggest Biden will likely win the South Carolina primary, and that the only question is what his margin of victory will be.

That’s good news for Biden, who has had disappointing finishes in 2020 Democratic primary contests thus far. Once the national frontrunner, he finished fourth in the Iowa caucuses, fifth in the New Hampshire primary, and a distant second in the Nevada caucuses.

He is counting on South Carolina to reverse that trend, allowing him to pick up much-needed pledged delegates (Sanders currently has a 30 delegate lead on him), and — ahead of Super Tuesday’s 14 primaries and one caucus — change the narrative around his campaign. A big win in South Carolina would be the most powerful argument the Biden campaign could make that he’s the candidate best suited to unite Democrats’ diverse base as the party prepares to take on President Donald Trump in the fall.

South Carolina is seen as a test of candidates’ ability to win over black voters

South Carolina is the first state in the Democratic primary calendar in which the majority of the electorate is black, and as such is typically seen as a test of candidates’ black support. It is a particularly important test for Biden, who has long said this key Democratic demographic makes up an important part of his base.

“All I know is, I am leading everybody, combined, with black voters,” Biden said at Vice News presidential forum in late January. “Name me anybody who has remotely close to the support I have in the African American community nationally.”

It is true that Biden’s black national support seemed unassailable in January, but that has changed in recent weeks according to a FiveThirtyEight analysis, with his average advantage over Sanders among that demographic now less than 10 percentage points. And as Vox’s Li Zhou reports, there’s a generational divide in Biden’s support — older black voters are much more likely to back him.

Still, in South Carolina, the former vice president is leading among black voters as a whole — an East Carolina University (ECU) poll taken February 23-24, for instance, found 34 percent of likely African American primary voters supported Biden, compared to the 24 percent who supported Steyer, and the 22 percent who supported Sanders. (The poll has a margin of error of 3.37 percentage points.)

Buttigieg and Klobuchar have struggled to win black support so far — and it would appear they continue to do so in South Carolina. ECU found Buttigieg to have just over 2 percent support from black voters, while Klobuchar received 0.4 percent.

Given that South Carolina’s electorate is 60 percent black, these numbers present serious challenges for both candidates. (They also present strategic and narrative concerns for both campaigns down the road — more on that later.)

Warren, whose base of support also tends to be less diverse, is doing slightly better than Klobuchar or Buttigieg among black South Carolina Democrats — her black support in the ECU poll was about 6 percent. Again, however, such a level of support means it will be difficult for her to compete with Biden, Sanders, and Steyer for delegates.

The frontrunners in South Carolina are Biden, Sanders, and Steyer

The vice president’s confidence about his chances Saturday is in marked contrast to how he described some of the previous races. He admitted during the New Hampshire primary debate that he fully expected to lose that state’s primary, saying, “I took a hit in Iowa, and I’ll probably take a hit here,” and didn’t bother to stick around to watch the results come in with his supporters. Instead, he left — for South Carolina.

It was a signal of just how important the state is to Biden’s campaign — in fact, Anton Gunn, Barack Obama’s 2008 South Carolina political director, told Vox’s Li Zhou that South Carolina is literally make-or-break for the former vice president.

“If Joe Biden wins by a small margin, then I think his campaign is on life support,” Gunn said. “If he comes in second or worse, I think he’s done.”

How large a margin Biden might win by depends on the poll one is looking at, but polling averages suggest a Biden victory could be the largest percentage-point win of the 2020 primary cycle so far — RealClearPolitics’ polling average puts him 12.6 percentage points ahead of Sanders.

The polls are clear — Biden is the state race’s frontrunner. And he received an important boost Wednesday: an endorsement from Rep. James Clyburn, one of Congress’s most powerful black Democrats — and a man seen as a kingmaker in the state.

Sanders has nevertheless gained ground in the state in recent weeks — his RealClearPolitics polling average spiked on February 12, the day after he won the New Hampshire primary.

Richland County vice director Dalhi Myers, who began the primary cycle a Biden backer and now supports Sanders, told Zhou that Sanders’s successes so far (he also won in Nevada) have captured the attention of many South Carolina Democrats.

“People aren’t going to vote for someone who can’t win,” Myers said. “If you’re the most electable, you’re going to have to get elected somewhere.”

One particular difficulty for Sanders is that polling suggests he will not be able to rely on what has been a key demographic for him in past contests — young voters. In New Hampshire, for instance, Sanders received more of the youth vote than all of his rivals combined. But Monmouth’s work found 31 percent of respondents between the ages of 18 and 49 backed Biden, compared to the 18 percent of 18- to 49-year-olds who said they plan to vote for Sanders. Other polls, like ECU’s, also found Biden leading Sanders among young voters.

Closing Biden’s lead both among young voters, and South Carolina voters generally, will require Sanders to pick up last-minute support from what polls suggest is a significant number of undecided voters. Monmouth’s pollsters, for instance, found 15 percent of likely voters hadn’t yet decided on a candidate as of last Tuesday, and weren’t yet leaning towards anyone.

These undecided voters also present an opportunity for Steyer, who is battling Sanders for second place. South Carolina marks the first contest in which the entrepreneur has been considered a frontrunner, in part because he has invested heavily in the state. He’s spent more than $18 million in advertising in there. And he has been praised for his strong canvassing operation, as well as his practice of hiring black businesses for campaign work.

“If you’re black, you probably get two to three mailers from Steyer a week,” Democratic strategist and former Booker campaign adviser Clay Middleton told Zhou. “I even saw his commercial on the weather channel.”

The effort has paid off in the polls for Steyer, but it is not clear it will allow him to do well enough to pick up delegates.

South Carolina’s 54 pledged delegates will be awarded both based on the results statewide and in its seven congressional districts. To get pledged delegates — either statewide or in the congressional districts— a candidate must clear a threshold of at least 15 percent, with 19 delegates available to those who meet that criteria statewide and 35 on offer to those performing well enough on the district level.

Candidates who don’t reach 15 percent support will receive nothing; those who do will split the available delegates proportionally based on their share of the vote.

Whether Steyer clears the 15 percent mark depends on the poll, and his RealClearPolitics polling average is around 14 percent, making it unclear whether he can expect to receive any delegates statewide. His polling would seem to put him in strong contention for receiving delegates on the district level, particularly in districts that play to his strengths. District 6, for instance, has more women than men, a large black population, and a large population with a median income of less than $50,000 — all groups with which Steyer has support approaching 20 percent, according to Monmouth’s work.

Any delegates Steyer receives in South Carolina would be his first. He is unlikely to receive enough to become the frontrunner, but a strong showing could give him enough delegates to surpass Warren’s current total of eight, and would put him in a competitive position for at least some of Super Tuesday’s contests.

South Carolina sets the nation up for Super Tuesday

Super Tuesday is in just three days, and candidates will be competing for 1,344 pledged delegates. Billionaire and former New York City Mayor Mike Bloomberg will be on the ballot for the first time, and the effect his $500-million advertising campaign will have on the race will become apparent.

But Bloomberg’s impact isn’t the only unknown — it’s also difficult to predict results in a number of primaries due to a lack of polling; Alabama’s last 2020 presidential primary poll, for instance, was taken in July 2019.

That makes South Carolina an important harbinger of contests to come. As my colleague Li Zhou has explained, “Historically, at least four Southern states — Alabama, Louisiana, Georgia, and Mississippi — have voted for the same Democratic nominee as South Carolina, giving this candidate a windfall of delegates.”

Should Biden have a decisive win in South Carolina, expect his campaign to regain some of its lost steam, possibly picking up wins in not just those four southern states, but collecting a sizable delegate haul in places like Texas as well. Similarly, a strong showing from Sanders would burnish his frontrunner status, boosting his argument that his coalition is more diverse than his 2016 one. And a better-than-expected showing from Steyer could give him momentum, particularly given he has made considerable financial investments in Super Tuesday states.

While Super Tuesday following so closely on South Carolina’s heels means the state’s winners can expect benefits, it also gives the state’s losers little incentive to drop out, as they hold out hope for quick reversals of fortune.