I don't particularly care or worry about the 20-25% of the population who still approves of Bush. They're lost causes.
What does concern me, if you believe the polls, is the 25%-ish of the population who disapproves of Bush but is planning on voting for McCain. I am baffled by them! When has there been any indication that McCain will change the direction that this country is going in? Not in 2006, when he voted for the Military Commissions Act, which lets the president authorize pretty much everything. Not in 2007, when he voted for Bush policies 95% of the time. Not in 2008, when he explicitly voted against a ban on waterboarding.
He even hired Bush's speechwriter from 2000 (start at about 4:50):
(In a related note, Jason Jones has been growing on me!)