Seems to me that the Democrats who have switched to the GOP are rarely troublesome. It's the homegrown Northeastern (either in geography or mindset) Rockefeller Republican types - people who've been registered R since they started voting - are the ones causing most of the problems.
Ronald Reagan was a Democrat early in his career too
Good point; there was a TX Democrat who switched in 1995, and Ron Paul took him out in the primary in 1996. Gingrich and GWB were against Paul.
I am willing to give him the benefit of the doubt. His record seems to back up his words.