Mitt Romney got to be the front runner in large part by being gaffe free--something you see in the NBC News-Facebook debate. He doesn't doze off like Rick Perry or get caught up in the legality of condoms like Rick Santorum. As I've written, he learned from his father's famed gaffe about undergoing a "brainwashing" by militiary and civilian officials on a visit to South Vietnam in 1965. (The elder Romney turned against the war.)
The whole insider-outsider debate is basically absurd. Romney has been running for office for years and his family was as political as you can get. Even his mom ran for Senate, running against the late Phil Hart, the Democratic Senator of the eponymous Senate office building. Romney doesn't get derailed.