How the caucuses work

The caucus starts at 7:00 local time for the Dems and 6:30 for the Republicans, so result will start coming in after 7:00. (That's 8:00 Eastern time.) ABCnews.com will be posting results in real time with a searchable database of exit polling updates.

To back up a second, the ultimate goal of any presidential primary candidate is of course to win enough party delegates to the national convention to gain the nomination.

Iowa seemingly doesn't matter too much by that calculation. Only 57 of the 4,051 total Democratic delegates and 40 of 2,380 total Republican delegates are at stake in Iowa. And since they are caucuses and not primaries they don't decide anything. They only elect delegates to a higher-level meeting, at the end of which is the state party convention.

The next few paragraphs break down the actual process in detail.

For the Democrats, delegates are elected on Jan. 3 to county caucuses. (There are 99 counties in Iowa, all of roughly the same size.) The winning candidate on Jan. 3 for the Democrats will be the candidate who wins the most of 2,500 delegates at stake. This is why Congressional Quarterly writes, "In the 2004 Democratic caucuses, Kerry’s reported total of 37.6 percent reflected his anticipated delegate strength at the state Democratic convention. It did not mean that Kerry was supported by 37.6 percent of all Democratic caucus attendees." In other words, the percentage reported on the Democratic side will be delegates, not actual voters. Each precinct has a certain number of delegates, based on how many people voted there in the top-of-the-ticket (president, governor) race in the last two elections. So it's conceivable that a candidate could turn out more voters and yet lose in the delegate count, if the new voters turn out more heavily in precincts that have less delegates. In 1988 for example, Gephardt won the delegate count but we're not sure if he actually won the most caucus-goers.

The delegates elected on Jan. 3 then got to the next step, county caucuses. On March 15, the Iowa Democratic county caucuses elect delegates to the next step, district conventions (the districts are the five congressional districts). On April 26, the district conventions choose 29 delegates to the national convention, as well as 3,000 delegates to the state convention. On June 14 the state convention chooses 28 delegates to the Democratic convention (16 of them are "pledged" to support a candidate, and 12 are "unpledged" party leaders).

For the Republicans, instead of the complex procedure the Democrats use caucus night (described below), everyone just puts the name of their preferred candidate in a hat. It's called a "straw poll." They also elect delegates to county conventions. Those are held March 1, and they chose delegates to the (Congressional) district conventions. Those are then held April 26, and their only job is to instruct the delegates to the state convention which presidential candidates the district delegates prefer. On June 13-15 the state convention district caucuses meet, and select 15 delegates to the Republican national convention (three per Congressional district). They are allocated proportionately. Finally, the state convention is on June 14, which elects 25 delegates to the national convention. 22 of them are pledged (proportionally) to candidates, and 3 are unpledged party leaders.

Whew! You see why the media skips over the boring details and just report winners and losers. That's why Iowa is so important--for the media spectacle. It's the first presidential voting anywhere, so the winners get to look like winners and get lots of free media throughout the country.

So what's going to happen in this first round of caucuses?

Here's a good graphic on how the precinct caucuses work. There are 1,784 precincts in Iowa. Some of them are so small they have to combine with other precincts.

Here's a description of the process for Republicans, from HuffPo:

The Republicans have an actual paper ballot. It doesn't list any candidates... [they] just write in whoever you want. There's a little speaking time where folks makes a short pitch for their candidate, then you vote. It's a secret ballot, with none of the standing in front of the neighbors and bargaining that the Democrats have. This means second choices matter less to Republicans than they do to Democrats.

After voting is done, the Republicans count up their votes and call a touch-tone hot line in Des Moines to report the vote count results. "Ronald Reagan 76 votes, Abe Lincoln 44 votes, Eisenhower 27 votes, and Nixon 1." Unlike the Democrats, where a precinct's impact on the caucus result is frozen based on a delegate count, higher caucus turnout in a Republican precinct means more influence on the outcome.

Once the votes -- remember, "straw poll" votes, they're called -- are counted, the delegates are elected by all the caucus goers who choose to stay. Then the caucus moves on to election of party officers and debate of the platform, just as the Democrats do.

Here's what the Democrats do, from NPR:

Unlike a primary — where your vote is private — in a caucus, you declare your support for a candidate in plain view of everyone around you. Candidate Smith's supporters go to this corner of the room, candidate Jones' that corner, and so on. If no candidate at a particular caucus site receives the support of 15 percent of the attendees, his or her supporters need to form a coalition with another candidate's supporters to reach the vaunted 15 percent threshold. Otherwise, the candidate ends up with no support at all.

Here's a description of the vagaries of the Democratic process from John Fund:

Not all local caucuses are equal. The "entrance" polls of voter preferences that you will see reported Thursday night are likely to be from urban areas, which may shortchange candidates like John Edwards, Mike Huckabee and Fred Thompson, who have campaigned more heavily in rural areas. "It's entirely possible that John Edwards could come in a stunning second when all the votes are in, but the country will have gone to bed thinking he only took third place," says Howard Fineman of Newsweek.

Rural Iowa matters for another reason in the Democratic contest. In order to encourage candidates to campaign in farming areas, state Democrats have tilted the delegate allocation so that rural areas are disproportionately represented in the final results. This sometimes can lead to bizarre results. As Roger Simon of Politico.com notes, "the turnout in some precincts is so small that a single family--let's say four people--can determine the winner. In other precincts, only one person will show up and win for his candidate by being the only person in the room." In small-turnout caucus meetings, ties are resolved by a coin toss or drawing lots. In 2004, four precincts saw literally no one show up to vote in the Democratic caucus.

Iowa is even more important this year, because in a very short period of time (a little over a month) there is a ton of delegates who will be chosen. For instance, for Democrats, Super Duper Tuesday features 22 states with 2,075 delegates, more than half of the Democratic total. As I've argued, Super Duper Tuesday might be too big to matter.

Here's some notes on the calendar after Iowa.