McCain would NEVER pick Romney. Lieberman.....Feingold.....he’ll go to a friend from his past.
Lieberman would probably rather stay in the Senate, and I doubt he would help McCain much in terms of winning the election. Apart from the war on terror and related questions, he’s pretty much a down-the-line liberal, but has very little support in the Democratic Party (his run for the nomination in 2004 was pathetic). McCain has credibility on national security and foreign policy—where he needs help is on issues where he has antagonized conservatives, and Lieberman would be worse than useless there.