Technically I'm not sure if it's legal to bet on the elections, but you can.
Why is this of interest?
We know from watching racehorses that the research and bets of gamblers are often a very good indicator of the possible outcome of a race. The folks at the University of Iowa have taken this to the next level by creating a gambling office where you can bet on elections. The idea here is not to make money, but rather, to research how accurately this system works.
Have a look at their site:
http://tippie.uiowa.edu/iem/about/
A of today (Oct 22 2012) here are the predictions on the presidential race: