Your first assumption that Bush will withdraw the troops from Iraq is flawed
Instead you will see the surge continue. The Congress will not muster enough votes to prevent it.
The Presidential Candidates will bemoan that they are going to be forced to fix Bush's mess... But they will offer little in they way of solutions until one brilliant Democrat, probably a late entering Gore, throws a hail-mary pass in his bid to be elected President by announcing he has "A secret Plan to end the War in Iraq!". The koolaid drinking Gorons will latch on to this "secret plan" and it will become another article of faith in the God-less religon of the Kook fringe.