Idea futures are interesting, so I went to tradesports.com to buy Kerry Futures contracts, since I believe pre-election polling is notoriously poor in quality. They were trading at 43 for a contract that pays 100 if he wins, and that seemed a good buy. By the time I could buy them (slow site, overloaded) they were 50 but now they are at 71. The bidders clearly have developed a strong reversal of feeling.
One source is the exit polls. While U.S. media are not publishing them, the CBC in Canada has few viewers in the USA and has no reason not to, and the news is good for the Senator, particularly in Pennsylvania.
Many have argued that idea futures with real money on the line are very good predictors. However people also clearly follow the polls, which is why Bush led in those futures for most of the election race, and even up to just a few hours ago. Still, Bush went south in these long before other sources so they're a good source as far as that is concerned. And perhaps I made a few bucks. (Not a lot, they limit you to $250 credit card if you do instant signup.)