DES MOINES, Iowa (AP) -- Presidential hopefuls urged their partisans to brave the cold and rally fellow Iowans to the caucuses Thursday, a massive test of organization that held the key to victory in the first contests of the 2008 election season. Capturing the urgency, and biting chill, in the air, Barack Obama implored his people, "Walk quick, talk fast."
Iowans, courted for months by candidates barnstorming their towns, swamping their airwaves and, in the later rounds, bickering with each other, finally give shape to the presidential race in a caucus ritual rooted in a centuries-old tradition of political activism.
Whether they would bring clarity to the national contest as it pivots to New Hampshire only five days later and then on to remaining states was just one more unknown in a campaign unpredictable at every turn.
"The two things that are clear to everyone here is that it's cold and it's close," said former Missouri Sen. Jim Talent, an adviser to Mitt Romney. Romney vastly outspent his GOP rivals, only to see his longtime lead in Iowa polls slip away.
The former Massachusetts governor goes into the caucuses fighting for a win against Mike Huckabee, a man who stood at 2 percent in the polls in Iowa less than six months ago and was a blip elsewhere too until his campaign took off.
Polls indicate an improbably tight three-way race for the Democrats, Hillary Rodham Clinton, Obama and John Edwards all knotted together - a crowd-pleasing nail-biter reflected in swollen crowds at Democratic venues and expectations of a hectic caucus night.
Caucuses begin at 7 p.m. and with that evening curtain-raiser, most candidates filled their Thursday calendar with still more speeches and events.
But while the talk goes on past one more sundown, the time for listening was fast drawing to a close. The persuasive power of rhetoric was suddenly yielding in importance to the availability of baby sitters to help people get to the caucuses.
Campaigns were ready with snow shovels if needed, and used the phone and Facebook online to encourage voters. Romney said his campaign made 12,000 calls on Sunday alone.
Obama, an Illinois senator, recommended longjohns as he sent people door to door. Clinton, in her historic run to become the first female president, served bagels, fruit and coffee to Des Moines volunteers and said of the single-digit temperatures, "I know if you're here from Iowa to help me, this is like, nothing."
Surveys suggested a quarter of likely caucus-goers were still undecided in the final days.
Clinton and Huckabee appeared on late night talk shows, a chance to start looking beyond Iowa and endear themselves with a national audience just as the campaign starts to move across the country.
But their different responses to the siren call of Hollywood illustrated the polish of the Democrat's campaign and the occasional muddle of Huckabee's, recurring more often in recent weeks.
Clinton, feet firmly planted in Iowa, spoke by tape with David Letterman, whose New York-based show settled with striking writers. Huckabee flew to Burbank, Calif., to sit with Jay Leno in the final crucial hours of the Iowa campaign and was unaware when he made the commitment that he'd have to cross a picket line. The former Arkansas governor said he supported the strikers; they called him a scab.
Obama, an at-times stirring orator and the most viable black presidential candidate in history, drew large crowds, yet acknowledged that won't put him over the top unless he can motivate his supporters to come to the caucus meetings.
He's proven especially popular among young people, who are notably less apt to vote.
Altogether, 120,000 to 150,000 people were expected to come to the Democratic caucuses and 80,000 to 90,000 to the GOP meetings. Caucuses are held in each of the state's nearly 1,800 precincts and draw anywhere from a few people each in rural areas to hundreds in suburbia.
Former Sen. Fred Thompson of Tennessee hoped to rescue his faltering candidacy with a third place finish against an ascendant Sen. John McCain of Arizona, with long shot Rep. Ron Paul and former New York mayor Rudy Giuliani also in the mix. McCain made a quick return to Iowa on Wednesday after largely bypassing the caucuses to make his stand in New Hampshire.
Giuliani, who has seen his national lead in polls wither, is pinning his hopes on the flood of contests after New Hampshire if he can't get traction in the Granite State, where Romney and McCain are going to head to head.
Edwards, who finished second in Iowa in 2004 on his way to a spot on the national Democratic ticket, mounted a 36-hour marathon capped Wednesday night at a rally with rocker John Mellencamp. The grueling schedule turned Edwards' voice hoarse.
At every stop, the former North Carolina senator tried to turn what some Americans see as a drawback - his lucrative career as a trial lawyer - into an asset.
"I spent 20 years in courtrooms" fighting big companies, he told an Iowa City crowd. "You cannot 'nice' these people to death," Edwards said, obviously jabbing at Clinton and Obama's greater willingness to negotiate for change. "They will stomp all over you."
Calvin Woodward reported from Washington. Associated Press writers Charles Babington, Beth Fouhy, Glen Johnson, Amy Lorentzen, Libby Quaid, Liz Sidoti and Nafeesa Syeed contributed to this report.