It’s a reminder that it was never Christie that these activists liked. What these activists liked was the reliable partisanship that he seemed to practice. When he didn’t act the part of the angry partisan that they were used to seeing, and instead acted as a self-interested politician and responsible state official would, they no longer had any use for him. The fact that he had been considered an effective surrogate for Romney over the last several months is quickly forgotten, and all that remains is the idea that Christie "betrayed" the cause by doing something that any other official in his position would have done.
First of all, I highly, highly doubt the hurricane or Christie's actions had any significant effect on the election. What I thought was interesting in reading Larison was what motivated Christie to act the way he did.
Being a reliable partisan is often a good way to act rationally. When I say act rationally, I'm assuming that getting reelected is the top ranked priority, or at least one of the highest priorities, for a politician. Christie's constituents were in trouble. So he acted to try and help them. And that meant working with Obama.
The people of New Jersey, and most everyone dealing with a situation like this, don't care about partisanship. At that point it's simply about protecting their life and property. Whoever can get the job done is who they will look to, and that happens to be the federal gov't. Republicans outside of New Jersey don't care about that. So when they pushed back at Christie for embracing Obama's help, Christie pushed back at them because his interests didn't coincide with theirs.
Even if Christie is interested in running for national office I think his actions make sense within a rational choice model. Having good partisan credentials is important when running for president. But given this situation, I think it was a smart move to value appearing to be a good governor concerned about his constituents rather than appeasing the Republican party.
I could be persuaded that Christie could have handled the situation differently around the edges. He can be assertive with the media, which I generally like. But for the most part I think what he did makes a lot of sense, and it happened to be the right thing to do for the people of New Jersey, at least as best as I can tell. And again, I think it's ridiculous to think this had any significant effect on the presidential election. That's just Republican spin and/or them refusing to accept reality.