what's a caucus?

Excerpts from Sarah Nussauer and Nick Timiraos in this weekend's WSJ, a helpful "primer" on Thursday's Iowa caucus-- and how it is distinguished from its more famous (and intuitive) cousin, the primary...

How do the Iowa caucuses work? The Iowa caucuses are different from primary elections, in which voters cast secret ballots at polls as they do in a general election. Caucus participants gather along party lines in 1,784 county precincts -- at a school, or even a home -- where they try to persuade fellow caucus-goers to support their candidate.

In a Republican caucus, participants can speak on behalf of candidates, after which votes are cast on blank ballots. Democrats gather in a corner of the room based on whom they support, so their decisions are public. Candidates who don't receive support from at least 15% of participants are "eliminated," but their supporters can realign with another group.

The article is not clear whether the 15% rule applies to both parties, but from Wikipedia's entry on this-- apparently, it is for the Dems only. Another difference, not made explicit by the WSJ article is that GOP votes are cast by secret ballot.

A final head count at the Jan. 3 gatherings will determine how county-level (not statewide) delegates will be apportioned. Neither party is nominating delegates for its national convention -- that requires several more steps that take months -- but caucus results have been regarded in the past as a bellwether for voter sentiment, giving winning candidates momentum and losing candidates more to prove going into later nominating contests.

How could those dynamics shape the vote? With no clear front-runner among the Democrats and Mike Huckabee showing a slight lead over Mitt Romney on the Republican side, the caucuses could hinge on turnout and on which candidates' supporters will be most persuasive in a crowd.

For Democrats, a voter's second choice can also play an important role because of the 15% rule. A poll taken this past week shows John Edwards is the second choice of 23% of Iowa Democrats, followed by Illinois Sen. Barack Obama, with 18% saying he is their second choice, and New York Sen. Hillary Clinton, with 16%. But 23% of likely Democratic voters say they have no second choice, according to a Los Angeles Times/Bloomberg survey.

It also will tend to lessen the prospects of Democratic minority candidates. If Biden et. al. are not able to muster 15% in many (if any) caucuses, they could be shut out-- despite having 5-10% of the vote. Beyond the practical implications of this, it's ironic that the Democrats are better known for protecting rights of minority groups-- and that their name is related to democracy rather than republic.