Nate Silver notes that since Rep. Joe Sestak (D-PA) announced he would almost certainly challenge Sen. Arlen Specter (D-PA) in a Democratic primary for U.S. Senate, the formerly Republican senator has voted with his new party on 28 out of 29 contentious votes, or 97% of the time.

“Specter’s overall party loyalty score since becoming a Democrat — counting votes both before and after the primary challenge — is 87%. This contrasts with the 44% of the time that he broke ranks to side with the Democratic on contentious votes while still a member of the Republican Party. He’s basically been behaving like a mainline, liberal Democrat.”
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