Now that Trump’s voters have heard a candidate who will speak to them in terms they can appreciate, the toothpaste is not going back in this tube. After betrayal by the Democrats and Republicans, they will simply wait around for someone to once again affirm their belief that the only thing a person really needs to believe in order to succeed is “America good, foreigners bad.”
The question the GOP needs to ask themselves is whether they want to be that party forever. I would certainly hope not; the experience of Europe suggests that such a party really tops out its national appeal at somewhere around 30%, even in the midst of a genuine migration crisis like the one Europe is currently experiencing. So unless the GOP is prepared to go back to the pre-WWI days of having less than 150 total members of Congress, the pain of losing this bloc of voters is something that should be risked now, rather than later.
And if these voters really are determined to force this implausible vision onto a political party, the GOP should at least force them to start their own infrastructure and forge their own way in terms of ballot access in all fifty states. Because the alternative is just to allow this latent third party to hijack their existing infrastructure for free, and toss the people who have built the party from the ground up out into the streets – all in the service of a man who a) isn’t conservative and b) will undoubtedly lose in landslide fashion.