I have a TL like this. It's called "A Miracle in Iowa"
I'll have to look up that one.
For this point of discussion, I would have to say the following.
1) Whether or not the revelation would cause Edwards to drop out depends largely on how close he is to the General Elections of '08, and how strong the evidence against him was. It is was not incredibly strong and the GE was getting pretty close, Party leaders might decide to just ride the leading edges of the storm as best they could and hope it came to nothing.
If they had more time, or if the evidence was pretty strong, then Edwards might have to bow out in favor of somebody else.
2) How does he do? I can't do a nationwide map, but against John McCain & Sarah Palin he would likely do quite poorly. We're not talking Nixon vs. McGoven in '72 here, but he would lose.