What’s more, in the past there’s been a tendency for party switchers to suffer from ideological drift. Jim Jeffords went from being more conservative than most Democrats to being solidly liberal, and Ben Nighthorse Campbell went from being more liberal than most Republicans to being virulently right-wing.You don't even need to actually change the letter behind your name for this to happen. We saw the same sort of pattern happen with Zell Miller, who became a virulent right-winger without becoming a Republican, and Joe Lieberman, who of course became Joe Lieberman.
What is the deal here? Here is what I think: Party-switching politicians drift ideologically because they need to reduce their own sense of cognitive dissonance about the switch.
Wikipedia (good enough for our purposes) defines cognitive dissonance as "an uncomfortable feeling caused by holding two contradictory ideas simultaneously" and explains it this way:
A powerful cause of dissonance is when an idea conflicts with a fundamental element of the self-concept, such as "I am a good person" or "I made the right decision." The anxiety that comes with the possibility of having made a bad decision can lead to rationalization, the tendency to create additional reasons or justifications to support one's choices.In the case of party-switchers, politicians have to reconcile the contradictory ideas that: a.) I am a principled, righteous representative of the people, and also b.) I have chosen for reasons of my own self-interest to switch my party allegiance.
How do you resolve that cognitive dissonance? With ideological drift! What better way to prove that "I am a good person" or that "I made the right decision" than by really believing in the ideas of the party you switched to?
I wouldn't hazard a guess about what Specter will do about EFCA or any other specific piece of legislation. But I definitely do predict that in general he will become a good deal more liberal than he was yesterday, and will almost certainly end up to the left of someone like Sen. Ben Nelson of Nebraska -- and who knows, maybe even considerably further left than that.
UPDATE [4/28 11:44pm] ... Nate Silver of FiveThirtyEight does the numbers on how far party-switchers actually drift and the answer is: significantly.