I touched on this earlier today in the article about Joe Biden’s “firewall,” but there really is something strange going on in South Carolina. This was brought more into focus for me after reading an article from James Joyner at Outside the Beltway today. It’s no secret that Biden’s previously massive lead in the Palmetto State has all but collapsed, and Bernie Sanders has been the largest benefactor of this shift.

But how much of a factor has Tom Steyer’s massive advertising campaign really been? Perhaps more than I first gave him credit for. And as Joyner points out, if this week sees an additional shift of only a few points, Biden could actually wind up losing the one state everyone was positive he would hold and the subsequent boost in momentum that he’ll need heading into Super Tuesday.

The CBS poll is the most recent included in the RealClearPolitics average for South Carolina and there are only three other recent surveys. But Steyer is in third place in all of them. If this bears out Saturday, Steyer’s presence on the ballot could either hand the contest to Sanders outright—effectively ending the race—or sap enough delegates from Biden to deny him any real momentum from a win.

The longer the “moderate” vote is divided among multiple candidates—and Bloomberg will join the fray in earnest on Super Tuesday—the more impossible it becomes to prevent Sanders from winning a plurality of delegates. But, as I noted yesterday, all of the candidates have an argument for remaining in the race.

All, that is, except for Steyer.

As I noted in the previous article, we’re not just looking at individual snapshots or possible outliers in South Carolina, but at trends that have been simmering for at least a couple of months. As recently as last Christmas, Steyer was stuck down at around 5% in South Carolina. But he’s really gone all in, flushing Bloomberg levels of money into television advertising there. (Heck, his wife actually moved to live in South Carolina last month, so there’s one vote he can count on at least.) In the past few weeks he’s moved up into the middle teens and one survey actually had him at 20 last week.

During that same period of time, Bernie Sanders has gone from 11% to 23% and his RCP average in South Carolina is currently only three points behind Joe Biden. Compare that to Uncle Joe’s numbers, which have fallen from a high of 45 last November to 24 today. That’s a pretty spectacular crash.

It’s not going to take too much more of a surge for Sanders or a bump for Steyer to leave Joe Biden in second place this Saturday. The one place where I disagree with Joyner is the overall impact this will have on the race. It would be bad news for Biden to be sure, but it will still be far too early to say that the blow would “effectively end the race.” There will still only have been four states counted and a small fraction of the total earned delegates claimed. We won’t be close to closing the books on this one until at least the day after Super Tuesday, if then.

Getting back to that RCP average in South Carolina, it’s equally clear that Bernie’s share of the total Democratic base has a lower ceiling than Biden or several others. If we think of Sanders and Warren as the socialist wing of the party (as opposed to the so-called “moderates”), their combined share in South Carolina adds up to 31%. When you tally up the “moderate” support for Biden, Steyer, Buttigieg and Klobuchar, it’s 58.2%. That’s almost a two to one gap.

And South Carolina isn’t exactly an outlier in terms of the distribution of the various elements of the base. Even looking at the national polling, Sanders and Warren add up to a slightly better 42.5. But the combination of the moderates listed above (plus Bloomberg) is 51%. So the only thing keeping Sanders in the lead right now is the splintered nature of the moderates and the massive amounts of cash being injected into the primary bloodstream by Bloomberg and (to a lesser extent) Steyer.

Now, James Joyner himself admitted that nobody has much of a reason to drop out at the moment. But that can and probably will change after Super Tuesday. I don’t find it hard to picture both Klobuchar and either Buttigieg or Biden being gone. Warren should be out also, which will help Bernie, but a leaner moderate lane will cause him a lot more heartache down the line. Bernie should come out with an impressive delegate total on that Wednesday morning, but it still won’t be an insurmountable lead. And in a bit of irony, yes… it may wind up being Tom Steyer that forces Biden out the door, making life tougher for Sanders as we get deeper into primary season. And if the splintering continues for too long, I still maintain that a brokered convention isn’t entirely off the table yet. If that happens and the DNC (via superdelegates) allows Bloomberg to buy the nomination on the second round, the ensuing meltdown among the Democrats’ base will be both real and spectacular.