The Obama hate machine pumped out plenty of rumors about his nationality and religion ever since he became the Democratic nominee in 2004. He was a Muslim, he was Kenyan, white-people-hating aliens placed him on earth to destroy all mankind, etc etc etc. You know the stuff.
The best the Romney hate machine can ask is, "Is Mitt Romney a unicorn?"
Of course he's not. He doesn't have a horn on his head and if he did he'd probably have two. He is a dashing white (most unicorns are) and his hair is perfect (all unicorns have great hair). Everything besides those two facts points in the direction that he is not.
Unicorns generally have rainbow flatulence. Unicorns generally take a stand on issues and they're always right. Mitt Romney takes multiple stands on issues. You never know if he's right.
Let's make a rumor that cuts to the core. Is Mitt Romney a polygamist? No. He's not.
But that doesn't matter in politics. The truth is stupid. Is Mitt Romney a polygamist? Prove he's not.