If I was a Republican voter, I'd be looking at Trump and wondering if his election would be the worst possible outcome.
It seems likely that he will heavily tarnish, if not absolutely dissolve, the GOP brand - for possibly a generation. The party would be split into the Trumpian howlers who think white, male, nationalism is the answer to everything, and all those who at least pretend to be interested in governance (all those Republicans now pledging to vote for Clinton or Johnson, or to fight him in Congress, etc.). That would worry me, if I had positive feelings about the Republican party.
But if Clinton should win, the GOP would be utterly united ... in their hatred of Clinton. It would be the status quo for the GOP: knee-jerk opposition of the hated liberal. No, they wouldn't have the Presidency, but they also wouldn't have a fractured party ostensibly lead by an ignorant, childish, buffoon who would turn voters off the GOP brand for decades. That would offer me hope.