At The Monkey Cage, John Sides notes, “All in all, I am quite impressed by how much political science research speaks to Specter’s switch, and how well it helps us understand his decision and what may result from it.”
The upshot is that political science would appear generally to suggest that Specter will change his voting behavior towards substantial consistency with his new party. That would be quite contrary to what I heard a reporter for Roll Call say on WHYY radio earlier today (that he would not change “a single vote”, Arlen will still be Arlen, etc.).
Parties matter to politicians, and so they tend to switch to parties that are compatible with their goals, including ideological preferences. And, yes, parties matter in these (and other) ways even in the US Senate. (For that matter, even in Brazil, where switching for consistency in policy voting might be even more unexpected by conventional wisdom, and where party switching is notoriously common.)
Some pundits have already suggested an “ah hah” moment over Specter’s almost immediate post-switch vote against the budget resolution.* But it was a freebie for him. Budget resolutions can’t be filibustered and the measure had a clear majority without Specter. It was a perfect–and for Specter, perfectly timed–opportunity to demonstrate that he remains “independent.” But that vote should not be taken as predictive of how he will behave between now and the 2010 elections, or beyond.
* The linked item ends by noting that Sen. Judd Gregg, R-N.H., who brifly considered joining Obama’s Cabinet, said “”When you join a caucus, you have to vote with them most of the time.”