If you don't know about it, I suggest you start following
http://www.tradesports.comPolitical futures markets, where people bet real money, have historically been more accurate than polls in predicting election results. And, as far as I know, TradeSports has the highest trading volume of any political markets.
Click on "Politics" in the left-hand column. Then check out "Democratic Presidential Nominee."
Look at the number in the "Last" column to see the percentage odds, based on actual money being wagered.
Since a Clark contract has not been available, the "Field" contract represents him. (It means "someone else in the field".)
The odds right now are:
Clark 29
Dean 27
Kerry 16
Hillary 12
Lieberman 6
Gephardt 6
Edwards 3
If you click on the name, you can see a graph showing how their odds have fared in recent weeks/months. (Note that they use the DD/MM instead of MM/DD.) It's a British site, because gambling is not legal in the U.S., but most of the betters are U.S. citizens taking a small risk of being caught.
The odds had Kerry as the frontrunner for a long time. Dean overtook him a few weeks ago. And now Clark has overtaken Dean.
Also, check out their odds for Bush's re-election (63 right now). And the California governor's race, which has been fluctuating A LOT, but at this moment is Davis (recall fails) 41.9, Arnold 41.0, and Bustamante 28.0.
They also have odds on the Democratic caucuses/primaries, and the state-by-state odds in the 2004 election.
Put it in your favorites-- it's fascinating to watch on a daily basis.