I just don't see how reasonable people can continue to be Republicans if Trump is nominated. A member of the party of Trump is just not something an intelligent human being should want to be. The consequences of Trump's nomination go far beyond handing the presidency to Hillary Clinton on a silver platter; the moral stain on the party's brand will last for years and years if it ever goes away. The GOP will be seen as the "Crackpot Party" for the foreseeable future, and the Democratic radicals will run wild.
I will never understand how so many people can be so clueless. To paraphrase Churchill, never in the field of history have so many so thoughtlessly and so unnecessarily done such damage to their own cause, and to their country.