When I took the readership's temperature on various VP picks, Joe Lieberman did not come out on top. Far from it. At 26% acceptability, he was at the bottom of the heap.
I was one of those 26%. To me, he wouldn't be the best pick, but he wouldn't be the worst either.
There is much to commend the "do no harm" VP calculus. Lieberman wouldn't be a "do no harm" pick. If you do the static analysis (is Lieberman better than, say, Rob Portman?) it's all wrong.
The difference is that any of the conventional picks don't help McCain with his #1 priority: winning the election. Despite narrowing the gap, McCain is currently about 3 points behind. He needs a better VP pick than Obama will come up with -- and unless Obama chooses Clinton, Obama's pick will be safe and milquetoast. Lieberman is the most obvious opportunity to shake up the calculus of the race. Picking him did something for Al Gore in 2000, taking him from a sure loser to a position of strength in the fall. A conservative VP on a losing ticket is still a losing ticket.
Lieberman's endorsement of McCain was a turning point in McCain's favor in winning the primary. Republican primary voters did not recoil in horror that a Democrat would give McCain his stamp of approval. Much the opposite. It's very possible someone else would have been the nominee had Lieberman not endorsed. It's easy to see how McCain would feel a deep sense of gratitude.
Win or lose, Lieberman as the VP nominee would have the practical effect of forcing him to switch parties sooner rather than later. If you want to notch a Senate seat and prevent a filibuster proof Obama majority, this is one way of doing it. As part of the Republican conference, he'd start voting as a party line Republican most of the time, though not always.
Now, to the caveats. I certainly wouldn't Lieberman to be President. Unless the worst were to happen, there is not much chance of that. Lieberman is 65, so there is a real chance he would embrace the Dick Cheney model. But moreover, the Republican Party would never give him the nomination. In a sense, conservatives would be better off with Lieberman than with a base demoralizing Ridge or Crist as the heir apparent.
As for being pro-choice, I think we need to make a distinction between a pro-choice Democrat and a pro-choice Republican. A Tom Ridge pick could signal that the party itself is abandoing the pro-life plank. But can you say that in the same way if the nominee is not a Republican? A Lieberman pick would say nothing about where McCain wants the party to go. Lieberman isn't about the Republican Party, and wouldn't really even be in it as the nominee. He would be Switzerland as far as internal party battles go.
I'm not saying Lieberman is my favorite pick. But if McCain wanted to build buzz and throw long to win, Lieberman would be the way to do it.