I vote for Mitt Romney's "Who let the dogs out?" moment.

Classic presidential campaining... they take him out for a photo op with some young black people. They probably don't support him (or even maybe know who he is) and he looks uncomfortable in the situation. For know reason, he says "Who let the dogs out?". A very outdated reference that seemed to be done so he could "relate" to them.

http://www.youtube.com/watch?v=FDwwAaVmnf4