It could happen! The parallels to Watergate here are intriguing. Remember, it took years for Nixon's criminal insanity to play all the way out.
We've got the unpopular foreign war, the Veep about to be dragged down by a major scandal that will likely lead to his resignation, the incresingly paranoid POTUS, and the liklihood of all of it leading to a Democratic House and Senate in 2007.
Best case for Dems is they stonewall the SCOTUS process, letting the right fight amongst themselves and keep O'Conner on the bench this year as Shumer suggested. Then they filibuster any wingnut that comes along until Cheney resigns, then filibuster the VEEP nomination until after the elections. They get the congress back, start the impeachment proceedings, and then Bush resigns, giving us President Nancy Pelosi.
I love this scenario!
Ancient Chinese Curse: May You Live In Interesting Times...