Two mysteries right now in the early-early Democratic race.

1. Can Warren dislodge Bernie as the Great Progressive Hope via a barrage of big bold policy plans?
2. Can the white VP to the first black president top black candidates like Kamala Harris, Cory Booker, and potentially Stacey Abrams among black voters?

Lotta suspense around the first question at the moment, not so much around the second. Charleston’s Post and Courier has it Biden 46, Bernie 15, Harris 10 in its home state of South Carolina, where black voters made up 61 percent of the electorate in the 2016 Democratic primary. That’s a 14-point bounce for Biden since last month. How’s he doing it? Electability, mainly.

It also doesn’t hurt that Biden has a reputation as a moderate in a state where Democrats can run more conservative than other parts of the country, Furman University political scientist Danielle Vinson said…

Nearly nine out of 10 of those polled believe Biden has the best chance to topple Trump. Sanders was the only other candidate to win support from a majority of those polled. Harris and Warren were each considered potential Trump-beaters by about one-third of voters.

“Voters figure, ‘We know a white man can win the presidency,’” Vinson said. “Biden seems to be the safe choice.”

It’s not Bernie’s or Harris’s voters who are being stolen by Biden. Their numbers are steady, if weak. It’s Beto O’Rourke who’s in freefall, dropping from nine percent to two — tying him with ultra-longshot Andrew Yang. Maybe Beto was momentarily occupying the niche of “blandly electable moderate-ish white guy” until Uncle Joe bounced him out of it. Interestingly, Abrams has fallen nearly as much as O’Rourke, declining from seven percent as a hypothetical entrant into the race to one percent now. A sign that she’s overrated as a candidate or of something else? Hold that thought, we’ll come back to it.

This isn’t the only poll this week of an early southern state showing Biden zooming ahead thanks to support from black voters. One survey of Florida has him up 39/16 over Sanders there, with 46 percent of black primary voters in his camp and 85 percent rating him favorably. Harris and Booker are essentially nonfactors among the group even though, according to the pollster, they have 80 percent name recognition. It’s not that black Democrats in Florida don’t know them, in other words. They’ve heard of them. They just prefer Biden.

Politico has a well-timed story today about black members of Congress getting excited about a Biden/Harris “dream ticket.” That *is* highly likely to be the ticket if Biden’s the nominee, I think; it covers his bases on diversity and Harris’s credentials as a U.S. senator and former state AG will be more impressive to voters than Abrams’s history as a state rep.

“But for the fact that we have two of our own who are both quite capable of being president, I’d say probably a lot of the members [of the Congressional Black Caucus] would’ve already announced for Biden,” said Rep. Emanuel Cleaver (D-Mo.)…

“I said a few weeks ago that if [Biden] were to get in, everybody else would be running for second place. I said that over a month ago. And he got in, and the polls said everyone else is running for second place,” [James] Clyburn said in an interview…

“The data are clear that he has strong support among African Americans,” Clyburn said. “It’s just that simple. He’s had that for a long, long time, and he’s kept it steady so far.”

It would be a coup for Biden to land some endorsements from members of the CBC. I think most will stay neutral, not wanting to be seen as preferring a white candidate to Harris, Booker, or Abrams, but Biden can live with that so long as the general message emanating from the caucus is that it’s not an act of betrayal for a black voter to choose him over the others. Warm words from the CBC will also help him survive the beating he’s going to take from Harris and others over his role in enacting Congress’s crime bill of 25 years ago. That’s the issue with the greatest potential to drive a wedge between him and black voters — although even if Biden gets no help from Clyburn, Cleaver, or others on it, he can always remind people that his record on the bill obviously didn’t bother Barack Obama so much as to disqualify him from the VP hunt.

Right now he’s the only candidate in the race who seems to appeal to more than one “niche.” Not only is he cleaning up with black voters, he consistently does well with older whites and has lots of support among whites without a college degree. That was famously Bernie Sanders’s base in 2016 against Hillary, seemingly a sign that populist socialism was more viable among downscale left-leaning whites than any of the smart set believed. Biden’s leading with them now, though, despite the fact that he’s conspicuously more centrist on policy than Sanders is. Harry Enten argued a few days ago that working-class white support for Biden is one of the chief reasons that Sanders’s numbers have fallen in poll after poll since Biden got in. (Bernie’s numbers against Biden are actually better with highly educated whites than less-educated ones.) Apparently lots of blue-collar white Democrats prefer Uncle Joe to Sanders, even if that means postponing the socialist revolution.

But let’s come back to Stacey Abrams’s decline in South Carolina, which I noted above. Did she lose six points because her voters decided they liked Biden better, or did she lose six points because she’s been mostly off the radar for the past few weeks while Biden’s launch has dominated the news? What would happen if Abrams, who’s well known in neighboring Georgia, declared her presidential candidacy tomorrow? Before you answer, look back to the polls of the 2008 Democratic primary in South Carolina between Hillary and Obama. Hillary led consistently, sometimes by wide margins, throughout 2007. But once South Carolinians started paying closer attention to the race — and once black voters there began to believe that Obama really did stand a chance nationally — he blew past her. Between December 2007 and January 2008, he went from trailing narrowly to leading by double digits. He ended up winning by nearly 30 points.

Point being, if Abrams jumped in, galvanized voters, and proved in Iowa and New Hampshire that she was a top-tier contender with national strength, South Carolina’s Democratic voters could shift seismically, and very rapidly, from Biden to her. Same goes for Harris, I guess, although her launch has been sufficiently underwhelming that she’s now trying to “reset” her candidacy as a Trump attack dog and can’t seem to decide whether to play for progressives or centrists. Either way, though, no matter how big Biden’s lead in SC gets, it’s no sure thing. Ask Hillary.