For all this talk about party elites turning on Trump and what not, people seem to forget that Trump is still extremely popular among the Republican base.
Yes, I know that he's popular among the Republican base. I'm talking about the extent to which a previously little known primary challenger might get elite media coverage, to the point where people following the campaign would actually know who they are (unlike the primary challengers to Obama in 2012, who only the nerdiest of political nerds would be able to identify). I'm saying that if there are some Republican elites who are disillusioned with Trump, then they'll talk about a Republican primary challenger, even if it's someone in the mold of a McMullin or a Peterson, who might otherwise remain in obscurity.
I highly doubt the media's gonna focus that much time on an unknown challenger to Trump (especially because there's virtually no chance of Trump losing a primary) when there's an open primary on the Democratic side of things. But, we'll see.