As the world turned on Thursday to this unpretentious farm state for signs of who might be the next US president, it struggled to follow one of the most bizarre processes on the electoral map.
Local political activists were set to gather after nightfall at some 1,800 precincts, in school cafeterias, church meeting halls and hotel ballrooms, to pick their favorite Republican or Democrat presidential candidate.
"Now, you decide," a banner headline in the Des Moines register told Iowans, on a cloudless but frigid day, with stiff icy winds making temperatures of minus 7 C (20 F) feel like minus 15 C (5 F).
With the leading contenders on both the Democratic and Republican sides in tight races, candidates were doing everything possible to coax Iowans to go out and caucus.
Campaign workers for Democratic hopeful Hillary Clinton were distributing snow shovels, and like other campaigns offering lifts to get people out on a freezing night.
Campaigns have sent thousands of canvassers out into the state, knocking on doors, and using phone banks. Some candidates have been contacting supporters by email on Internet sharing sites like Facebook as well.
"We'll babysit for you, we'll drive you to the caucus, we'll shovel your driveway. We'll do whatever it takes," said Clinton campaign chairman Terry McAuliffe on Fox News on Wednesday.
"This is a big job, the next president of the United States of America is going to face. We want to make sure that ... you go out and take part in that process."
Iowa's Republican caucus is easy to understand, amounting to an in-person, secret-ballot poll of support for presidential aspirants.
But the process for Democrats is complex and fluid.
Democrat Barack Obama, at a Methodist church in Indianola, called the exercise "simple ... easy (and) exciting," but it is arguably anything but.
Iowans can turn up at a caucus intending to support candidate A, and end up, after an hour of discussion and debate, picking candidate B.
In full view of their peers, with no ballots in sight, activists literally vote with their feet for their 2008 champion -- gathering in corners of venues designated for each candidate.
And Democratic candidates, especially long-shots, face real indignity: if they don't reach a certain threshold -- usually 15 percent of a meeting's turnout -- they are declared not viable.
Their supporters are then asked to join the backers of another candidate -- meaning a candidate who is the second choice of large numbers of voters may eventually overcome a more popular rival.
Democratic leaders urge Iowans to have a second choice in mind just in case, and candidates themselves forge strange alliances.
Long-shot candidate Dennis Kucinich has told his supporters to back Obama as their second choice, due to their shared staunch opposition to the Iraq war.
The arcane caucus process serves to portion out delegates to county conventions, which pick state convention delegates, who finally vote on which Iowans go to national party conventions to formally designate the White House nominees.
In 2004, Democratic Senator John Kerry pulled off a surprise win in Iowa over favorite Howard Dean, and went on to win the nomination -- only to lose to President George W Bush in the general election.
Only 124,000 people attended those Democratic caucuses, giving ammunition to those from other states who say the small midwestern outpost has too much sway over the choice of US presidents.
But with the 2008 race the most open in generations, a record turnout, especially among Democrats, is expected this time around - even if it still represents just a fraction of the state's three million people.
Iowa's Republican and Democratic caucuses begin at 7 pm (0100 GMT Friday.)