As others have mentioned, the number for people who self-identify as gay is a little harder to get a handle on. 1-2ish percent seems to be the rule for face-to-face and mail interrogatories, but it’s higher for many phone polls and higher still for internet polls – as high as 6% for the internet, but of course that may reflect the demographics of internet users (and internet survey-filler-outers) as much as anything.
I don’t think Bush will really run with the idea of gay marrage. In 2000 he had Cheney supporting states rights in determining marrage and I don’t see how the situation has gotten worse for gay rights people since then.
What Kerry will run on the most is jobs. The easiest thing for Kerry to do IMHO is go for the look of the way it was before Bush. Because I think that the best thing he can do is simply point out all the things that has happened under Bush’s term and say that he prefers how it was with Clinton. IE “What part of peace and prosperity do you not like”. It would have been an effective slogan in 2000 and I’d say it can be an even more effective slogan now considering what has happened with Bush.