Big margin of error here (6.2 percent) but we have enough polling of the race nationally and from Nevada and South Carolina that I don’t see a reason to doubt the basic conclusion that Biden’s huge lead among black voters has crumbled. Sanders now leads by an average of 11.4 points nationwide; he’s pulling away in NV, up 14 there; and poll after poll of SC lately, including the one Ed wrote about earlier, has Biden’s lead very narrow.

Bearing all of that in mind, paint me a picture of how Joe Biden comes roaring into Super Tuesday — the big, probably decisive prize on the calendar — 11 days from now and knocks Bernie back on his heels. If Sanders wins Nevada going away, as seems likely, the “Berniemania” narrative afterward will drown any good buzz Biden might receive by finishing second. And that narrative will propel Bernie in South Carolina either to an outright victory or a surprisingly close second, which will deflate much of the Super Tuesday momentum Joe’s hoping to get out of the state. Realistically, I think, Biden’s chances at this point depend on a shockingly strong finish in Nevada, not South Carolina. If he surprises there, the media will shift to a “Biden comeback” narrative in the days before SC votes. That might in turn ensure a comfortable win in South Carolina. And those two solid finishes back-to-back really might make him a player on Super Tuesday.

But it all depends on tomorrow night. A tepid finish in Nevada, even a (distant) second place one, and it’s effectively over.

And needless to say, if the national trend among black voters that NBC/WSJ is detecting continues, it’s over regardless:

According to the newly released data, Biden has the support of 31 percent of black Democratic primary voters, while Sanders captures the backing of 29 percent…

[T]he close margin shows that Sanders has made inroads in a community previously dominated by Biden; aggregated data from 2019 shows that Biden led Sanders among these voters by as much as 30 percentage points in NBC News/WSJ national polls last year…

A combined 65 percent are either enthusiastic (20 percent) or comfortable (45 percent) with Sanders. For Biden, it’s a combined 69 percent either enthusiastic (16 percent) or comfortable (53 percent).

Head to head with Trump among black voters, Joe and Bernie are equally strong: Biden leads 89/8 while Sanders leads 87/7. Black voters are also less likely than the overall electorate to say they’re uncomfortable with a socialist candidate. So what’s left of Joe’s “firewall” here? The only good news for him here is that this poll was taken before Wednesday’s debate; maybe Bloomberg’s lousy night will convince some black voters to migrate over to Joe. But Bloomy will keep spending to win them back, and it’s an open question right now whether his debate performance will matter at all.

I wonder if even an Obama endorsement would save Joe should Bernie succeed in running up the score in Nevada tomorrow.

Imagine the best-case Biden scenario you can think of at this point. He shocks the world by winning NV, let’s say (never mind that he’s third behind Buttigieg in the most recent poll there), then wallops Sanders in South Carolina. He’s back in the game! Except … lots of Super Tuesday votes will have already been cast before tomorrow night’s Nevada results thanks to early voting. And where’s the money supposedly coming from that’ll enable a last-second Biden ad blitz in Super Tuesday states? Digest this:

While Sanders started February with nearly $17 million in the bank, according to campaign finance disclosures filed Thursday night, his next closest rival (nonbillionaire class) was Biden, at $7.1 million. Warren was closest to the red, with just $2.3 million left in her account, while Buttigieg ($6.6 million) and Klobuchar ($2.9 million) were in between…

Bloomberg, fellow billionaire Tom Steyer and Sanders are the only candidates with more than $1 million in television advertising time already booked in the coming days in Super Tuesday states.

It’s not merely that Biden hasn’t yet spent a million bucks on TV ads in Super Tuesday states. According to the WSJ, he (and Buttigieg) hadn’t booked a single ad yet in those states as of last night. The only campaigns not running on fumes financially right now are Bernie and of course the billionaires Bloomberg and Steyer. And so the only way Biden threatens Sanders on Super Tuesday is if there’s a big — BIG — wave of Joementum buzz after Nevada and South Carolina, enough to overwhelm paid media arranged by Bernie’s machine and the Bloomberg death star. The idea of it is farcical.

And even if Biden somehow managed to fight his way to respectable second-place finishes across a variety of Super Tuesday states, there’s still the thorny problem of catching up to and eventually passing Bernie in delegates before the convention. In theory the majority of Democratic voters will doggedly vote for him over the socialist this spring in state after state, month after month, seeding ever more chaos by slowing erasing the delegate gap between them. But in practice that’s not how it works:

If Sanders does take a large delegate lead on Super Tuesday, voters concerned about his electability should consider the possibility that the benefits of uniting the party (and turning its combined fire on Trump) by early spring would outweigh the costs of Bernie's liabilities.

— Eric Levitz (@EricLevitz) February 21, 2020

Biden would have to overcome that plus Sanders’s superior fundraising plus he’d have to neutralize Bloomberg, who can run for as long as he wants in hopes of engineering a brokered convention. C’mon. It’s over for Joe. And probably over for Bloomberg, although he may still be half a billion dollars or so away from figuring that out.