I haven't seen a single John McCain bumper sticker. Not a one. I'd say I see, on average, a Ron Paul bumper sticker every third day or so, an Obama bumper sticker slightly less often. But McCain? I'm still waiting to see my first one, so I'll know what it looks like. I live smack dab in the reddest state in the Union, albeit in the most liberal part of that state. Bush stickers in 2000, on the other hand, I saw lots of, and in 2004 I saw even more of them. It suggests rather strongly that McCain's appeal to the wingnut base is next to zero; I also believe it's a reflection of the realization many people, even wingers, have come to that the Republicans have fucked everything up, and the even greater realization that they are going to lose, and few people will go out on a limb for a loser. I'll bet there are plenty of McCain bumper stickers in Washington, DC, though, or there would be if the media people were allowed to put political bumper stickers on their cars.
I actually considered getting one and putting it on my car out of pity. Or I could make my own: "Vote McCain. Because somebody has to."
The Bush bumper stickers I used to see everywhere disappeared right around the time his approval rating hit 30%. Coincidence, I'm sure.