This, also many Republicans don't realize that Christie won largely due to Corzine and would have lost against, say, Codey or Pallone.
I don't think that's accurate.
Codey would have won, but that's a special case because he was a popular former governor. Christie was viewed as an incredibly strong candidate, one that New Jersey Democrats viewed in 2008 to be, by and large, unbeatable. I don't think Pallone would have have won.
Christie ran a pretty bad campaign and only barely beat the very unpopular Corzine. Someone who didn't have the baggage of being an unpopular incumbent almost certainly would have beaten him.