The last trade (as I write this) on a Dean contract was 0.725. That spike upward was probably a result of the reporting that Al Gore will endorse Howard Dean.
OK, what does that mean? It means that the last time there was a trade, somebody paid 72.5 cents on a contract that pays 100 cents (1 dollar) if Dean becomes the Democratic nominee and 0 dollars if he does not.
Another way of saying the same thing is that, among participants in this market, Dean is the odds-on favorite for the nomination.
The price is also up at
Tradesports.com, where the last trade was Dean at 67 cents, up 6 cents for the day. If you assume it's a "fair bet" among risk-neutral participants, you can also say that they collectively think there's a 2 in 3 chance that Dean will be the nominee.
Or did I just make it more confusing? :-)