The moment that took all of the air out of Mitt Romney’s 2012 campaign was when, in a debate with President Barack Obama, he dug into a peripheral issue that he thought was safe: foreign policy.

Romney threw all of his weight at Obama over the relatively limited attack on a U.S. embassy that had resulted in the death of an American ambassador. It blew up in Romney’s face when he demanded that Obama call the attack an incident of terror, only to be fact-checked by moderator Candy Crowley. She remembered that Obama had in fact referred to the event as an “act of terror.”