I have no idea what the weather will be like on November 2, but when I looked at conditions nationwide yesterday, it seemed to me there were more spots in the 80s and 90s than I'd expect for October.
So if there's a heatwave anywhere come November, let me suggest a slogan to use: "It's too HOT to vote Republican!" Perhaps some habitual conservative voters might be convinced to stay at home, in the cool.
And if the slogan catches on at all, by 2012 it might morph to shirts saying "I'm TOO HOT to vote Republican!"
(Note: Yes, I'm aware that individual bits of weather are not proofs of climate change. Six word slogans are seldom good for conveying subtle points.)