Keep these two numbers in mind.
150,000 -- if turnout is significantly above that figure for Democrats, then Democrats say a victory for Barack Obama is almost assured. If it's 150,000 to 135,000, Democrats think that Clinton will win. If it's at 135,000 or lower, then Edwards is the man...
80,000 -- High turnout on the Republican side benefits Mike Huckabee; lower turnout benefits Mitt Romney.
This article available online at:
http://www.theatlantic.com/politics/archive/2008/01/as-caucusing-begins/51437/