Quote from Epic:
I actually think that a big factor in this is desperation in the GOP. Not the candidates, but the voters. They are desperate for something different next fall. This desperation is causing an extreme amount of second guessing. If any candidate even appears weak at all, he is discarded in favor of another. If that candidate has a weak moment, then he is discarded.
A couple months ago the field was large so they could cycle through potential nominees and the swings weren't quite as dramatic. Now that the field has narrowed, any shifting is going to be significant as the voters battle within themselves.
Complete desperation.