After 2012, the GOP as both parties do when they lose, did a study as to what they needed to do to try and win in 2016. They chucked all of that because the base line wants Trump. They don't like women in power, they believe in conspiracies, they don't want racial equality or at least don't like the idea of anybody who isn't white being treated the same as whites, and they have come to believe that they have been left behind and that the current administration has done nothing for anyone.
This is the problem, the Republican Party has become a shitty coalition of "useful idiots" that are controlled by a rich hierarchy trying to get them to vote against their own interests and the 2 decades or better of bad ideas, and grooming these people into a monster have come back to bite them. The Dems will surely hang Trump around the neck of those that have supported him and the party for years and years to come, and to me the only hope the Republican Party has is to actively work to get Trump supporters out. Stop catering to that message, stop campaigning to it, and push these fringe elements out. It's possible they go form their own party, but I don't think it gets very far. If Trump loses by a gigantic margin, it can't be seen as anything but a referendum on his type of politics and that it has faded in importance and power at the national level.