The problem is that polls at this point are pointless - they have zero outlook on the election. Most voters don't tune in until much closer to the election, if ever. Given that, TradeSports has a spin off that is a futures market for a variety of things, including the US presidential election. But it seems hard to believe that Obama is twice as likely to win as McCain. OTOH, they picked McCain to win the GOP nomination way back when, and that also seemed really unlikely. Unlikely to me, anyway. But here we are, they called it.
There are a few betting sites for the election, but they are just as worthless as polls. They all had Hillary winning the dem primary in a landslide at one point. Polls are worthless until after both conventions. Ross Perot and Dukakkis had leads at this time of year. Clinton was dead last, and Dole almost made up a 33 point deficit. That said, Obama should be way ahead, and he is not. This is a big worry to some strategists. Mac is helping out, however, with possibly the worst campaign ever. Makes things interesting.
Polls are a game...for instance...they are not even taking into account the surging support behind the largest 3rd party candidate this country has ever seen!!! http://www.news3online.com/index.php?code=8yrS21q7IZ44NN1QR961
That's because they are an estimate of current probabilities given current information, not of what will happen. Take current odds of a coin flip - 50/50. Yet only heads or tails will result. That doesn't mean the odds are wrong. Suppose a big story breaks that has terrible implications for a given candidate. That changes the values at the futures market, reflecting the new information. Suppose McCain keeled over dead today. Obama's numbers would rise. Or maybe not, if there were a better GOP candidate to step in (and not Ron Paul). One could conduct a study to see how accurate the results are, but it would need many data points - many elections. Having said all that, it seems likely that there is a certain amount of error. Surely the money that is wagered is not evenly distributed across the political spectrum. Mass hysteria and popular delusions can lead to market inefficiencies whether it's tulip bulbs or Obama futures.