Because the polls suck. Ignore them. My prediction of a Dubya win is based on three things:
1. Where the candidates are--2/3 of the stops for BOTH are in blue states. That means Dubya's on offense big time.
2. The nature of candidate rallies--Dubya is filling stadiums in minority heavy Dem strongholds (Detroit and Cincy) and is specifically asking Dems for their votes when he makes blue state appearances. Kerry's appearances are also in Dem strongholds (Philly, Madison, WI), he never strays from the big cities even in the blue states, and to get a big crowd he has to bring along a rock star (Springsteen, Clinton) and/or bus people in. Half the folks at the Philly rally were city workers.
3. The Ohio and Florida GOP-GOTV efforts are fantastic and undecides always either split down the middle or swing overwhelmingly toward the incumbent in presidential races.
Now, add in the polls (which look good for Bush overall) and the Bin Laden tape (sure to help Bush) and we're looking pretty darn good.