There's a reason we'll support OBA (Anybody but Obama) and that is because nobody that uses logic and reason in their contemplative process can imagine a worse President the your dear leader. Of course, if you stick purely to emotional thinking, he's your guy.
The problem with an ABO philosophy is that you end up failing to properly scrutinize who it is that you are voting for in order to vote against a particular individual. You could very easily end up with a candidate who is nearly as bad as Obama (think McCain, Romney, Palin, etc....) simply because you were willing to assume that nobody can be as bad as Obama.
Personally, I have no interest in voting for ANY candidate for ANY office if I do not believe they are very close to my own philosophical viewpoints. That's why I end up checking boxes in so few of the individual election races.... because I can't support either candidate.