A 45 state victory for Bush would basically mean that he would have to win states like Connecticut (if Lieberman isn't the nominee), New Jersey, Delaware, Maryland, Illinois, and California (add Vermont if Dean isn't the nominee). Right now Gallup has Bush's approval rating at 50 approve/47 disapprove, the lowest of his presidency (actually equal to where he was about 2 months ago). Certainly things could turn around, but until they actually do start turning around politically for Bush, it's a bit premature to suggest that he's going to win any kind of landslide reelection.
The polls are usually taken among registered voters, but Republicans have higher turnout historically, so a poll parity of 50-47 suggests a voting advantage of up to 55-42. I doubt Bush could win 45 states unless everything goes as planned for him, which is not impossible but probably the worst case scenario for Democrats. It will take a real leader coming out of the primaries next spring to develop a forceful enough platform that middle Americans can start to embrace.