The only question I might ask of Christie is "why didn't you dig deeper into it upon hearing about it?"
The question I would ask Christie, is "Governor,
who told you this was a traffic study?" (Presumably the answer to that question would be Bridget Kelly, but the public deserves an answer to that question.)
The one enduring political problem that Christie has with this, (even if he had no involvement with it whatsoever or with any kind of post-action "cover-up",) is that he made some very poor choices in terms of hiring some people for important positions who had atrocious judgement. Whatever else to this there may or may not be,
that's an established fact. Christie himself has acknowledged as much.
However, if that's all there is to it, it's not impossible to recover from that. The American people are a very forgiving people, (that's why celebrity media apology tours are so popular) and if there's nothing more to this, and he makes the case, (as he did to a certain extent in his press conference) saying,:
"Yeah, I hired some people who let me down and acted inappropriately, and I take responsibility for that. I'm human, I'm not perfect. The current President has made mistakes too. The question isn't whether or not you will make mistakes, the question is how you handle them once you've made them."
That's basically the way he has to handle this. The bad news for Christie is that this will be an enduring aspect of any Presidential run. The good news for Christie is that there's still a lot of time, and if this is all there is, he can bounce back and even possibly help himself with the base in the primaries, since he is certainly no longer a "darling" with the press. (The fact that the mainstream media has been piling on and obviously been trying to take him down over this, will serve him as a badge of honor in that context.)