Here's one of my theories: Nader runs with Dean on his ticket. Not to be out done, Kerry/Edwards chooses Hillary as VP. The Democrat party splits, and GWB wins in a landslide- but Hillary becomes the figurehead of the Dems.
The other theory: Hillary sits all of this out, and watches, and then swoops in Dec 04 to be the new savior of the Democrat party.
Either scenario has Hillary coming out the winner, and the new leader of the Dems.