I'm sort of sorry this thread died down while I was gone, not because I think we need one more thread for partisan back-and-forth, but because the topic of the OP is really interesting to me. Granted, it's a little partisan in nature but you could still be a Democrat who thinks the contemporary GOP is solid and here to stay, or a Republican who thinks the Tea Party is leading your own party off a cliff.
Anyway, here's a good piece a few days ago from Jonathan Cohn:
http://www.newrepublic.com/article/1...e-theories-why
I think he nails it on point 3. The folks driving the GOP Crazy Train don't have their incentives aligned with the rest of their party, let alone the nation. There's probably a dose of 1 -- even if they recognize how toxic their views are right now, they're convinced the rest of the nation will come around eventually. But none of that matters if you don't win the primaries, you can't win the primaries without money, and the way to get money from the right wing is to out bat**** everyone else. There's really not much personal downside, if you don't mind living in an economy that you yourself have wrecked (and on that point, they are delusional).