They don't have one, and they can't stop Trump. They just have to hope that he implodes. If Trump actually wins the nomination, the Republican Party will actually just get worse (just like Goldwater pushed the party to the right, Trump will push it in a different direction). They will become a protectionist party, centered around nationalism and nativism. No longer a party of big business, but a party that serves the interest of the native population and its 'national interest' abroad.
"Worse".
Yes, much worse.
Interesting to see so many on a supposedly centre-left forum standing up for corporatism over representative democracy.
It's still a center-left forum. TWO people quoted me, and one was a Republican, haha.