I was going to say Obama too, but you really can’t know. If Obama had an affair with someone, would that turn off his base? Probably not.
If Romney had an affair, then yes, that would turn off his base.
Or if Rudy turned out to be a man...
Possibilities:
Hillary and Bill sleep in the same bed after all.
Michelle Barak’s comment about how “stinky” her husband is in the morning leads to revelation that they aren’t legally married, and she is a lesbian.
Romney has another polygamous wife somewhere with other children.