Bush probably has the election if it were held now. But if he signs the extension of the "assault weapons" ban, I could see enough pro 2nd amendment voters staying home on election day to cause him to lose. And they are a group of people who will not buy "Dean/Clark/Kerry will be worse" argument. How many people would have had to have stayed home in 2000 to throw the election to the other party? I don't think Bush can afford to piss off very much of the base this time around.
Or go dem. As in slighly over 50% of union member gun owners who voted for Bush last time. (West VA, Yoopers)