1.The Democrats and Republicans have two completely different caucus systems.
The GOP takes a straight straw poll — secret ballot with one person, one vote. Whoever gets the most votes win. Simple. Democrats do it differently: Participants form "Presidential preference groups" by moving to different parts of the room. There is no secret ballot (which for some of us suggests that pressure and intimidation might just occur every once in while). The candidates who can't garner 15 percent are considered "non-viable" and their supporters either go home or may realign with more successful candidates. So the second choice of caucus-goers can prove decisive.
Democrats don't use the one-person-one-vote system. Each of the 1,781 precincts gets a certain amount of clout, depending on how big the Democratic turnout was in the last Presidential and gubernatorial contests. So if, for instance, Sen. Clinton turned out huge numbers in Cedar Rapids, it wouldn't be truly measured by the Democratic system — she'd get the same percentage of delegates whether 200 or 2000 people participated. In other words, it's very possible that the candidate who turned out the biggest number of participants statewide could lose — if an opponent's strength was spread more widely.
2. Turnout is really low compared to turnout in primaries.
If the caucuses produce an all-time high of, say, 250,000, that would still equal little more than 10 percent of eligible voters. The New Hampshire primary, by contrast, produced a 44 percent turnout in 2000, the last time both parties had contests. Why? Simple — there are no "polls" open all day; if you can't show up on time, you don't play. There are no absentee ballots; no early voting. So what the caucuses measure is the intensity of support. You need commitment to leave your home in the dead of winter for two or three hours.
3. The caucuses have been "berry berry" good for the Hawkeye state.
Apart from the $60+ million the candidates spend, and the countless millions spent by the media army, Iowa gets way more than its share of political pandering. Just one example, offered by a writer whose name I wish I remembered, ruminating on the subsidies for the highly inefficient corn-based ethanol. "If Idaho had the first caucuses," he said. "they'd be subsidizing gasoline made out of potatoes."
And for more on the inner-workings of Iowa caucusing, check out Greenfield's CBS Evening News caucus explainer.