I’ve been writing all week about the surge of Joementum in South Carolina but the sheer scale of it in polling makes it more surprising by the day. SC has always been his best early state, of course, the “firewall” where Biden has never once relinquished the lead since entering the race last April. (Bernie alllllmost caught up to him seven days ago.) But for all his strength there, he’s only rarely crossed the 40 percent threshold in polling. Before this week, the last time he’d done it was early November. The previous time before that was early October.

He’s done it twice in the past 24 hours.

In one of those polls, from Emerson, he leads by 16 points. In another, Trafalgar, he’s ahead by 21. He’s right on course for exactly the sort of blowout win he needs to revive his candidacy and maybe give him enough buzz to produce a stronger-than-expected showing on Super Tuesday. Which would make the March primaries meaningful, not the Bernie walkover that seemed assured after his own blowout win in Nevada last weekend.

According to [Trafalgar]’s crystal ball, Biden leads among likely “First in the South” voters with a whopping 43.9 percent of the vote – easily outdistancing Sanders (22.8 percent), Steyer (10.5 percent), Buttigieg (9.6 percent), Klobuchar (5.9 percent), Warren (5.6 percent) and Gabbard (1.7 percent).

The email indicated the survey was conducted between February 26-27, polling 1,081 respondents with a margin of error of plus or minus 2.99 percentage points.

Only once since last June had Biden touched 44 percent in a poll. His polling average of 39.7 percent at RCP today is the highest he’s ever had in SC. He’s peaking at the perfect moment. There’s even an outside chance that the polls are lowballing him:

While there *have* been polling errors this large in primaries past—think Michigan 2016!—a Sanders win would be a big-time upset. On the flip side Biden could run up the score. In 2008 (Obama) and 2016 (Clinton) the SC winner won by a much BIGGER margin than poll averages showed.

— Nate Silver (@NateSilver538) February 29, 2020

With a big enough win tonight, in fact, Biden would briefly hold the distinction of leading the race in terms of both national delegate totals and total votes received:

For instance, with a 25-point win and a turnout of 400K, Biden would net 100K popular votes over Sanders and become the popular vote leader. He currently trails Sanders by 95K in the aggregate national popular vote.

— Nate Silver (@NateSilver538) February 29, 2020

That’ll change dramatically four days from now once Bernie runs up the score in California, but “new frontrunner” will be a sweet talking point for Biden ahead of Super Tuesday. His biggest problem since Iowa has been the growing perception that Mr. Electability can’t seem to actually win anywhere, and thus isn’t worth investing in. South Carolina’s about to change that and maybe encourage swing voters in other primaries next week to roll the dice on Joe too. In fact, to see at a glance what sort of effect Biden’s shocking rise in SC has had on the overall nomination picture, eyeball the first graph in FiveThirtyEight’s South Carolina forecast. A week or so ago, Sanders was approaching 50 percent odds of winning the nomination via a majority of delegates. As Biden gained new life in SC polling, though, Bernie’s odds plunged. The most likely outcome right now is a brokered convention (52 percent odds), with Sanders clinching down to just 32 percent.

What happened in South Carolina this past week to send Joe through the roof? What did he say or do to convince so many late deciders to break his way? Nothing, possibly: It might be a Bernie backlash, as SC voters realized that a vote for Sanders tonight would all but end the primaries. This NYT article adds an interesting second dimension, though. Black Democrats know that Iowa and New Hampshire are grossly unrepresentative of their party demographically; if they rubber-stamp Bernie’s victories in those states by handing him another today, they risk marginalizing themselves as a force within the party. A vote for Joe, in other words, is a vote to flex their electoral muscle, to show the field that black Democrats are a major constituency that can and will strongly influence the outcome of the race.

More broadly, in interviews with African-Americans across the state this past week, many said they were eager to send a message to the national Democratic Party: that their views on electability — which candidate is best suited to beat President Trump — would not be shaped by outcomes in the predominantly white states Iowa and New Hampshire, which backed former Mayor Pete Buttigieg and Senator Bernie Sanders in contests earlier in February.

“We’re the base, and we’re yet to express ourselves,” said David Cakley, a church deacon from Goose Creek, S.C, referring to black voters. “Biden needs a boost and we’re going to give it to him.”

Mayor Stephen K. Benjamin of Columbia, S.C., who has endorsed the former New York City mayor Michael R. Bloomberg, summed up the urgency for black voters in this primary by quoting a line from the Atlanta rapper André 3000: “The South got something to say.”

Will the south as a whole have something to say on Tuesday? There are seven southern states up for grabs, but according to FiveThirtyEight’s model, right now Biden is favored to win just one of them, Alabama. He’s being weighed down by Mike Bloomberg’s presence on the ballot in the other six. What effect will a blowout win tonight have on voter preferences between Biden and Bloomy in those? Some votes are already banked via early voting but 72 hours of Joementum hype could shift remaining undecideds towards Biden on Election Day.

Which could mean *a lot* in determining whether Bernie wins this race outright or has to fight for it on the floor of the convention.

We’ll have a better idea of all this in six hours or so. There is, of course, the possibility that the good polling this week for Biden will backfire: Expectations are now so high in South Carolina that even a mildly impressive Biden win of eight points or so, say, will feel like a minor disappointment. He needs to run up the score. But if he does, who knows what sort of Super Tuesday polling we’ll see on Monday — or what sort of fundraising windfall Biden might see from the anti-Bernie brigades? His cash flow has improved recently, and some of the movers and shakers who’d been frozen while they wait to see whether Biden or Bloomberg is their best bet against Sanders might come away from tonight believing that Joe is clearly the moderate with the best chance. (Especially given Bloomberg’s polling downturn lately.) Stay tuned.