Campbell wasn't a liberal either. He was a true centrist, unlike Lieberman, who's just liberal in domestic issues and conservative in foreign policy. Don't get me wrong, if he wanted to switch, I'd take it, but I don't see it happening.
Here is why: The D's know its a possibility. They know he can yank the rug out from under them at any time. Because of this, he's the most powerful Senator in the Senate, and he knows it. He can blackmail the D's to get whatever he wants out of them. So why would he switch? If he does that, he risks being marginalized in the unfortunate event that the D's gain in 2008. He keeps the most power by staying on the D side with the option to switch if they pi$$ him off too much.
That said, if he did switch, it would sure be interesting to watch the media throw a fit...and somehow justify why they threw a fit this time and not when Jeffords switched.
Good points. I don't trust Lieberman anyway; remember, he ran as Al Gore's VP.