History (and common sense) suggest that it will be the GOPe fielding a 3rd party candidate to throw the election to Hillary (or Biden).
Consider that if Trump does win the GOP nomination, he will be the first non-establishment backed candidate to do so since 1980. And how did the GOPe respond back then?
They assigned the RINO John Anderson to run 3rd party to throw the election to Jimmah Carter! Who at the time held the distinction of being the worst President in US History.
Fortunately, their plan failed only because the GOP candidate was so vastly superior to Carter and Anderson.
In fairness, I don’t think the GOPe was responsible for John Anderson. He was probably funded by leftists looking to split the Republicans. The GOPe were all in for Reagan once Bush was on the ticket. Reagan didn’t want to include Bush, and fought the idea initially, but uniting the factions probably helped a lot in the general election. Where he made the mistake was in bringing in Bush people like James Baker and not dumping Bush in 1984. He, like a lot of people, thought that maybe he had convinced Bush that his way was better, after he turned the country around. Then, the poor old Gipper had to sit there and listen when Bush told us he was going to give us a “kinder, gentler nation”. As though wealth creation and jobs are not kinder to people than a handout and perpetual poverty. But I digress.