On the eve of the Iowa caucuses, PredictIt.com has the probabilities of victory for the candidates as follows. These odds are likely to fluctuate over the next few hours. There is slight share inflation (because of the inconvenience of having money "tied up" on shorting long shots) so prices don't quite add up to 100%.

Iowa Democratic Caucus:

Clinton: .68 (67%)

Sanders: .34 (33%)

Iowa Republican Caucus:

Trump: .66 (62%)

Cruz: .32 (30%)

Rubio: .5 (5%)

Paul: .2 (2%)

Carson: .2 (2%)

The current nomination odds are:

Republican Nomination:

Trump: .47 (42%)

Rubio: .31 (27%)

Cruz: .13 (12%)

Bush: .8 (7%)

Kasich: .5 (4%)

Paul: .4 (4%)

Christie: 2 (2%)

Ryan: .1 (1%)

Carson: .1 (1%)

Romney: .1 (1%)

Democratic Nomination:

Clinton: .72 (69%)

Sanders: .28 (26%)

Biden: .5 (5%)

O'Malley: .1 (1%)

Each individual "market" on PredictIt is a yes/no event; for example, will Julian Castro be the Democratic nominee for Vice President in 2016, or will the Republican presidential nominee win at least 370 electoral votes in the 2016 general election. These markets work exactly like a stock market does; users place an offer to buy (or sell) a yes or no a certain number of shares for a given price, and if there is a match for their offer, they end up with a "no" or "yes" share for that event. For example, you can currently buy a yes share of Donald Trump sweeping the first four states (IA, NH, NV, SC) for 49 cents. If he wins all four states, your share is cashed in for a dollar, and if he does not, your share is valueless.

Prediction markets like PredictIt provide an interesting view of the "wisdom of crowds." Nate Silver famously relied on a similar prediction site, InTrade, for his 2008 and 2012 election analysis, particularly in the primaries. You can follow the odds for Iowa and the nominations, as well as hundreds of other markets, most of which are political, at: 

https://www.predictit.org/Browse/Featured