Remember after Republicans took the house in 1994, a lot of Democrats switched the party.I know of five: Billy Tauzin, Nathan Deal, Greg Laughlin, Tommy Robinson, and Jommy Hayes.
That doesn't seem like "a lot" to me, but we all have our own perspectives obviously.
I don't have precise breakdown on House/Senate Dems that switched. However, I have this:During the Clinton-Gore years 479 elected Democrat officials switched to the Republican Party. Since GWB was elected, 25 elected Democrat officials have switched to the Republican Party. Stats current as of Feb.2002. Nothing approximating these figures has occurred since Civil War.