The problem will more likely come in 2016*, by which time the GOP will...well, probably have still purged everyone, since the Movement is now master, but will likely have better narrative and media presence, and maybe even a couple of rising stars, at the same time everyone will be tired of Obama's shit and the Democratic Congress basically signing off on every law designed to run the country into the ground.
That is where thing's get interesting, once the Democrats manage to de-legitimize themselves. Will people turn back to the GOP then? It's a possibility that can't be ruled out. Third parties will likely gain something, but the idea that the ONLY VALID CHOICES EVAR are the GOP or Dems are so hardwired into the media and current political landscape the only people I can see benefitting from a Democratic collapse would be the Republicans.
*Or wont, because the earth blows up