He could call himself a Republican but you would have every level of the Arizona party repudiating him. One headline a day over the summer. They came close before. He dislikes Bush enough to throw a spear in his direction every once in a while but would he run with the party that is making a mockery of his greatest achievement, CFR?
A national campaign would also bring to light some questionable mafia connections. Some that he doesn't even know about.
In my heart of hearts I don't think anyone knows who Kerry will pick. I just don't think it will be ANY of his primary opponents. He really needs something that will light a fire under his party and the media. All he is getting right now are very conspicuous yawns. You are probably right about McCain but it would still be a big splash. How long it would last is another question.