Romney has been attacking Gingrich for being a "career politician." Chait expects the attack to be ineffective given Mitt's political history:
The point of the outsider anti-politician pose is that Americans dislike political ambition. They think politicians are grubby and self-interested, and have a higher view of people in other professions. That’s the power of the attack. When you’ve conceded that you wanted to be a career politician but you failed, and so you luckily managed to pick up different experiences, you’ve lost all the punch.
The Dish 