It’s been a heady month for Ben Carson. For a guy who, at times, barely seems like he’s actually running for President (but definitely seems like he’s running a pretty good book tour), it must have been bizarre to see himself catapult to the top of the polls and actually put an end to Donald Trump’s 100-plus day reign as the undisputed leader in the GOP polls. The last eight days, however, have seen this happen:

The entirety of Trump’s uptick at the end can be explained by the fact that RCP has chosen to use a rolling model of the four most recent polls, and an ABC/WaPo poll was released this weekend whose numbers look pretty wacky and the net result is that Trump’s showing of 32% in that poll bumped off a previous poll that had him at 22%, which resulted in an instantaneous rise of 2.5% overall on average. However, that poll did not hurt Carson’s standing, as it had him at 22%, which is actually the highest value of any of the four polls in use right now.

Here, in fact, are the Carson results for all the polls taken since the CBS/NYT poll that first showed him with a national lead:

From this chart we can observe a couple of things. First, Trump’s support has remained relatively consistent in the 22-28% range. These people, we have to assume, are mostly resistant to facts or reason, at least at this point. For the moment, they are where they are going to stay. They also aren’t growing in number, however. Trump remains at the top of pretty much every “would not vote for” list, so while his floor might be 20%, his ceiling might be 30%.

Carson, however, has been the wildcard in this race. There is a sizeable contingent of the GOP electorate that is disgusted with the status quo ante (for good reason) and has been looking for a home that does not have the word “Trump” emblazoned on the front in giant letters. Carson clearly caught these people for a couple weeks, but it looks like there is real movement right now that has seen a substantial portion of Carson’s support defect and split pretty evenly between Cruz and Rubio. In fact, in the latest Fox news poll both Rubio (14%) and Cruz (14%) have almost caught Carson.

Carson started the year with between 9-10% national support, so those folks will likely be with him until the point that he drops out or becomes obviously not a viable option. But if he drops down to that number prior to Iowa and his current followers continue to split roughly half and half between Rubio and Cruz, then you have basically the dynamic that we have been predicting here since September – Cruz v. Rubio for the final nomination.

The first domino to fall, though, of necessity, either Trump or Carson’s support has to crumble. Carson’s support has always been assumed to be softer and we may be seeing the first signs that this is actually true. Carson’s lack of readiness to answer national security questions in an election that increasingly looks to be a foreign policy referendum may have been his undoing. Of course, Trump’s answers haven’t been better or more knowledgeable, but these are not matters about which his fans have ever cared in the first place.