Stuart Rothenberg is an analyst and columnist for the beltway publication Roll Call. He's also the father of the Rothenberg Political Report, and a contributor to CNN. He suggests that John McCain's 'perfect' choice for VP would be his colleague Joe Lieberman:

Lieberman’s selection to McCain’s ticket would send a clear message about bipartisanship and about McCain’s desire to change the way things are done. While the Democratic nominee surely will talk about bringing people together and “change,” a truly bipartisan McCain-Lieberman ticket would trump any and all Democratic rhetoric.

The selection of Lieberman would have particular appeal to independent voters, who are likely to be a key swing group later this year...

But wouldn’t social conservatives, in particular, go bananas, since Lieberman is moderate or liberal on most issues other than Iraq? He supports abortion rights, generally votes with organized labor and is an unapologetic environmentalist. Conservatives would revolt, wouldn’t they?

Probably not. While there would be the usual fist-pounding from some “movement conservatives,” their anger at the selection would quickly dissipate when they saw the fury unleashed by liberals and Democratic bloggers.

Rothenberg gets a lot right here. One thing he fails to point out is that assuming Barack Obama is the Democratic nominee, McCain may have more of an opening to win over Jewish voters who rarely vote Republican. Lieberman would likely be a significant boost to that effort, and could give McCain a tiny edge in states like Pennsylvania and Florida.

I'm not suggesting you bet on Lieberman, but it would scramble the race, wouldn't it?