The hopeful case for Republicans concerned about Donald Trump’s persistent lead goes something like this:

At this point in the last Republican primary, Rick Perry was pulling away from Mitt Romney. He briefly opened up a 10-point lead, and then just as quickly gave way to pizza magnate Herman Cain, who in turn gave way to Newt Gingrich, and so it went until Romney cleaned up in the end. Yes, Romney polled better than Jeb Bush is currently polling, but Romney was pretty much alone among establishmentarian candidates, while Bush is splitting that share of the primary electorate with two or three other candidates. Likewise, in 2012, the reactionary share of the vote was about the same as it is now—larger than the establishment share—but it wasn’t enough to win then, and it won’t be enough to win this time around.

The differences between the 2012 and 2016 fields makes this rosy scenario hard to envision. Which is why Republicans are having a harder and harder time articulating scenarios in which Trump becomes a non-issue before the primaries, for reasons that don’t involve nativist GOP voters undergoing a sudden, collective epiphany.

For this race to play out like the last one did would require a series of increasingly unlikely assumptions to come to pass:

1) That the establishmentarian field winnows sooner than later.