Another term for preventive war is aggressive war - starting wars because someday somebody might do something to us. That is not part of the American tradition.
I like Mitt Romney as a person. I think he's a dignified person. But I have no common ground on economics. He doesn't worry about the Federal Reserve. He doesn't worry about foreign policy. He doesn't talk about civil liberties so I would have a hard time to expect him to ever invite me to campaign with him.