1. He's a fat slob with a New Jersey attitude (I'm fine with both of these, by the way), and his "shtick" would not have played well in any swing states.
2. He didn't stand a good chance of bringing his own state into the Republican column in 2012.
3. His career in elected politics has been less than three years in the governor's office in one of the most reliably dysfunctional states in the U.S.
4. His prior career as a Federal prosecutor might have played well in a campaign year where "law and order" were major campaign themes, but not in a year like this where the economy is front-and-center on the national scene.
5. New Jersey's unemployment rate is nearly 10% -- which is more than two points above the national average. Christie still has plenty of work to do in New Jersey.
Personally, I don't think Christie's plans have changed at all. He's going to run for re-election in 2013, and if he loses (or even if he wins), he's going to be angling to serve as the U.S. Attorney General in a second Romney term. He may even be a potential candidate for this post in January 2013.
I think that he went around for two years talking about how he wasn’t ready to be President might have made for some good commercials.