I think when the choice becomes Trump or Clinton, he will back Trump. He won't campaign for Trump or anything like that, the endorsement will be a formality.
I was starting to think, of course he would. But stuff is probably getting personal enough, that he won't. The question is, then, what does he do? He'd never endorse Hillary outright. But would he give in on his treasured principles? Would he actually hate Trump enough to give a wink wink Hillary endorsement? Would he just keep his mouth shut (thats hard to imagine)? I guess he probably would, because most of his supporters will.