DES MOINES - The applause grew as Democratic Sen. Barack Obama of Illinois called out the litany of his Polk County precinct captains in his first rally of the New Year.
"I love these guys," Mr. Obama said, gesturing toward the young people - men and women; black, white, and Asian - who stood smiling behind him. "They look like a Benetton ad," he joked.
The presidential candidates planned to criss-cross the state today, continuing a frenzy of last-minute campaigning. But by 6:30 this evening, they will have done everything they could to court Iowa's support. Then, in 1,781 precincts across the state, activists like those who joined Mr. Obama on stage will have the last crucial opportunity to deliver a win for their candidates.
At another rally last week in nearby Carlisle, Iowa, former President Bill Clinton called for a show of hands from the precinct captains in the crowd packing a middle-school gymnasium for a rally on behalf of his wife, Democratic Sen. Hillary Rodham Clinton of New York. "I don't want to put any pressure, but the future of the free world is on your shoulders," the former president said, with a degree of irony that was tough to determine. "We're all out there hanging on the thread of your efforts."
While most Iowa Democrats will have made up their minds before they arrive at tonight's caucuses, bartering and maneuvering during the community meetings can alter the totals at the margins - enough, perhaps, to reorder the results of an agonizingly close race here, and, with it, the overall dynamics of the road to the White House.
The task of the ground troops is simpler but equally crucial for Iowa's Republicans, whose caucuses, with their straightforward voting, more closely resemble a traditional primary or straw poll. For the GOP, the job of the grass-roots organizers ends when voters get to the door. But their precaucus organizing, targeting, and identification of supporters parallels the Democratic efforts.
On both sides, the key to caucus success, as an Iowa political mantra has it, is to "organize, organize, organize - and get hot at the end."
All day yesterday, at places like the downtown headquarters of Republican former Arkansas Gov. Mike Huckabee and the suburban campaign offices of Republican former Massachusetts Gov. Mitt Romney, banks of phones reached out to voters and urged them to show up at tonight's community meetings.
Mr. Romney has built an organizational effort that even opponents acknowledge is the deepest of the GOP field. Mr. Huckabee, the party's other leading contender in Iowa, is depending on the more diffuse efforts of voters organized outside the formal campaign structure, in groups such as evangelical Christians and home-schoolers.
The three Democrats leading in polls have also established ground games with reputations - to be tested tonight - as the most extensive and expert in the 36-year history of the modern caucuses.
Still, organizations divorced from basic political appeal are bricks without straw, as the experiences of former Vermont Gov. Howard Dean and former Missouri Rep. Richard Gephardt demonstrated four years ago.
Both Democrats had well-funded and what were perceived to be well-prepared organizations. On a frigid caucus morning, an army of Dean volunteers braved the cold to wave the campaign's blaze-orange signs along roadways across the state. But the show of support proved hollow, as Mr. Dean fell to third, while Mr. Gephardt's labor-dominated cadres managed only a disappointing fourth.
But political appeal allied to organizational groundwork is a potent combination.
After the candidate exited the New Year's Obama rally in Des Moines, canvassers reported to tables grouped by state legislative districts, where they were handed street lists and door-knocking materials.
Standing by one table, Bill Burton, Mr. Obama's press secretary, said the lists were a product of months of cultivating sources, including state Democratic party lists and the campaign's efforts in identifying and cataloguing information on sure and potential supporters.
"We know where our supporters are, and we know where the undecideds are, and we have the resources to target both," said Mr. Burton, as volunteers headed out into the single-digit cold to contact both.
In addition to the core task of identifying voters and making sure they show up, organizers and precinct captains have a vital role in shaping the caucus results under the arcane rules of Democrats' neighborhood meetings.
The first task comes after the caucus assembles, and supporters of the various candidates group themselves at different spots in the room. Individual precincts can award different numbers of delegates, depending on their size and voting performance for Democrats in past elections.
If a candidate does not have enough support in the room to win a delegate - a typical precinct threshold is 15 percent, but that can vary - he or she is not viable. Supporters of nonviable candidates can remain uncommitted or join the camps of other candidates, making them targets of opportunity for more successful campaigns' precinct captains.
In conference calls with reporters over the weekend, David Plouffe, Mr. Obama's campaign manager, maintained that his campaign's polling showed the Illinois senator to be well positioned to win second-choice support. But Mr. Plouffe acknowledged that the Edwards campaign also showed strength as an alternate choice.
On Tuesday, one of the race's other Democrats, Ohio Rep. Dennis Kucinich, urged Iowa supporters to migrate to Mr. Obama in precincts where Mr. Kucinich is not deemed viable. Four years ago, many Kucinich supporters ended up supporting Mr. Edwards after a precaucus accord between the campaigns.
A finer wrinkle in the caucus process involves how rounding the numbers of caucus-night supporters translates into delegate numbers. It can work out, for example, that one candidate has more supporters than he needs to be awarded two delegates, but not enough to win a third.
Another candidate, by the same token, may have enough support for one delegate, but be just short of the total needed for two.
Savvy and agile precinct captains will keep track of such arithmetic and exploit it to their candidate's advantage. A Clinton captain, to suggest a hypothetical example, might be willing to shift one or two of its spare supporters to a group favoring Delaware Sen. Joseph Biden if that would break a tie for a delegate between Mr. Biden and Mr. Obama, since the Clinton camp sees Mr. Obama as a greater overall rival.
"Every precinct captain has a calculator," an Edwards captain said. "I make sure I have my math guy with me."
Such horse-trading can be crucial, since the percentages reported tonight for Democratic candidates refer to the percentage of state convention delegates won - not the raw percentage of supporters at the caucuses.
The Block News Alliance consists of The Blade and the Pittsburgh Post-Gazette. James O'Toole is a staff writer at the Post-Gazette.
James O'Toole can be reached at: firstname.lastname@example.org, or 412-263-1562.