I doubt Rudy or anyone else would get in the race just to weaken another candidate, but seriously, do we really want to play these games?
Rudy is really not much of a conservative. Economics, foreign policy, defense, he is probably fine. Unfortunately, his liberalism/libertarianism on social issues is a terrible weakness. We need a candidate that can unite economic and social conservatives. Alienate social conservatives and we will not win in 2012. Giuliani is simply not an acceptable candidate.
But an establishment Rino would have a great shot at VP.
Rudy and Mitt remember Reagan had to have his Bush Sr.