This seems to happen much more rarely in this direction than from Dem to Rep:

https://en.wikipedia.org/wiki/List_of_American_politicians_who_switched_parties_in_office

To confirm, a GOP house member switching to independent or libertarian would also count?

@NicoDelon Yes. Anyone who leaves the caucus counts.

@BTE Seems to have happened to only 24 house members, in any direction, since 1876.

@NicoDelon Thank you for sharing that link. Never before has a minority group sabotaged or taken the party hostage like this. Don't discount he idea of Republican members simply getting fed up and resigning or retiring at the end of the term neutralizing the most potent threat against this move which is being primaried.

@BTE Oh I don’t deny that’s possible or even somewhat likely. I just needed to calibrate myself and so looked it up.