It's possible that the parallel universe created by the Right has gotten so complex that it's become exclusionary. I've tried to get a handle on this before, though I don't think I've quite managed to pin it down yet. I've mentioned before that it seems that members of the movement Right demand that their candidates buy into the Entire Package of Wingnuttia. This isn't simply political purism, it's about validating a worldview. There are all these articles of faith in wingnuttia which have been given to them by the wingnut noise machine, and failure to embrace them all is a signal that you aren't really part of the club.
But this wingnut worldview has gotten complex and sprawling. Its cast of characters, bizarre understanding of history, and policy positions have grown and expanded so that only obsessed true believers can really feel a part of it. They've established an entire mythology, and its adherents have become cultlike.
The noise machine still has a great impact on our mainstream discourse, but only the real hardcore wingnuts can really identify with the full wingnut package anymore. The beast has grown too large.