Well,
I should have been a little more specific. I would vote for either Hitlery or Obama over McQueen, but would prefer Hitlery. Hitlery is the most polarizing and most hated of the three. Republicans of all stripes WILL unite against her at every step. They would against Obama, but with rather less vigor, because he is a likable, amiable young guy (and they wouldn't want to be seen as racist). They wouldn't at all against McCain, because he is one of their own.
The media will judge Hitlery far more severely for her misdeeds than they would either Obama (because he is a black Muslim) or McCain (because he is a nonpartisan "uniter").
Best-to-worst-case scenarios (in order of best-to-worst):
--Hitlery
--Barack Osama
--McCain