the media will discredit it. that is the main obstacle, the white house let the bleeding go on too long, they allowed the media to set in the minds of most americans that the reasons for going to war were all false. its going to be very hard to overcome that, 160 days before the election. not that I am saying he shouldn't try, but its not going to be easy.
I can imagine the first debate when Kerry makes his charges about Bush lying about WNDs, and Bush responds with facts that haven't been publicly disseminated yet.