From Salon's War Room, this little tidbit from A.B. Culvahouse, the lawyer who led McCain's vice-presidential vetting process:
One other interesting point from Culvahouse's talk: Connecticut Sen. Joe Lieberman, a prominent supporter of McCain's during the campaign, was apparently a serious contender for the vice-presidential nod. But, because Lieberman is not a registered Republican, there would have been legal issues in some states.
"Five states have sore loser statutes... [making] it very difficult for someone who's not a member of the Republican Party to become the vice presidential nominee if they only switch parties to become a Republican shortly before the convention," Culvahouse said, according to Politico's Jonathan Martin. "So you were looking at going to the Supreme Court, which is not particularly appetizing."