Priebus says that it is unlikely that an alternative candidate will emerge at the convention but he isn’t ruling it out.
The Republicans are probably devising a “super delegate” system like the Dems for next time. If there is a next time for the current RNC crowd. (Which if the GOP wins is unlikely. Consider that.)
(From The Weekly Standard)
“Can you guarantee that the nominee would be one of the three in the race right now?”
Priebus responded: “Well, I mean, I think it would be highly unlikely if it’s not, um, I can tell you that. I think it would be somewhat, very unusual. But I can’t 100% guarantee that. I can’t imagine right now sitting here, believing it would be anyone but the three remaining candidates.”