I don't think that will happen. McLame will never, never, never get the GOP nomination. He's finished. He'll go Independent and try to take GOP/Dem 'moderate' votes. Rudy, while a nice guy, has too many problems with his liberal tendencies on abortion, stem cells, etc.. Newt has no chance with his baggage. Tancredo is a one-issue candidate, and that never works.
I think the only real race is between Nick Romney and George Allen. If I had to hazard a political winds guess for the future, I'd give the edge to Romney for the nomination. The only sticking point for him might be that he's a Mormon; but at the end of the day, that is not going to effect his general electability.
I also do not think Her Thighness will get the Dem nomination. I think it might be Russ Feingold.
I hope it'a Russ Feingold. It would be a fair fight and a very clear choice.