Iowans cast the first votes of the 2012 battle for the White House on Tuesday in an unpredictable ballot that could winnow down the field of Republicans vying to take on President Barack Obama.
After a months-long campaign onslaught -- barrages of television attack ads, telephone calls and mailings, candidates blitzing across the state -- Iowans headed into hundreds of caucus sites around the mostly rural heartland state.
Frontrunner Mitt Romney, 64, was locked in a neck-and-neck race with Representative Ron Paul and former senator Rick Santorum in the party's first nominating test, which kicked off at 7:00 pm (0100 GMT Wednesday) in places like school gymnasiums, libraries, and church basements.
The Iowa caucuses come against the backdrop of a sour, job-hungry US economy that weighs heavily on the embattled Obama's bid for a second term, four years after he promised "hope and change" in his historic 2008 victory.
"He's out!" Romney, a former Massachusetts governor and millionaire venture capitalist, told cheering supporters at a rally in Des Moines, Iowa's capital, in the final countdown to Tuesday's caucus. "I will get America working again!"
Results were expected hours after Iowans from the state's 1,774 precincts gathered in small groups to hear speeches from their neighbors on behalf of the seven candidates in play here.
"A lot of people are going to walk in still trying to decide what's the right thing for America," former House speaker Newt Gingrich, who trails in the polls, told CNN. "So, I think we could win."
The quirky process does not directly award delegates to the party's nominating convention this summer, and its strength lies in its timing: It can set the tone for the rest of the state-by-state battle, lift or bury a sagging campaign, and add luster to a shining presidential prospect.
Santorum, a fierce social conservative who surged in Iowa after once being given up as politically dead, predicted on ABC television he would "do very well" here and then carry that momentum into New Hampshire's January 10 primary and then "pour it on" in South Carolina on January 21.
Romney has made little secret that he hopes for a strong finish in Iowa, a romp in New Hampshire, and another success in South Carolina, that may give him a lock on the nomination months before the November 6 general election.
Paul's unorthodox libertarian views have earned him a devout following, but he is seen as uncompetitive in other states, while Santorum, 53, faces an uphill fight to match Romney's massive national organization.
Still, while Romney's massive campaign warchest and high-profile endorsements have fed his image as the candidate to beat, he faces stubborn doubts about his conservative credentials, as well as his Mormon faith, and has been unable to increase his support among Republican voters nationwide above 30 percent.
Paul, 76, a small-government champion opposed to foreign aid and military interventions overseas, has accused the other candidates of supporting a foreign policy of "mischief around the world and policing around the world."
"Most of the rest of the Republican field seems to be a little bit over eager to use nuclear weapons and to bomb other countries," Republican Senator Rand Paul, the candidate's son, told CBS television.
The candidates made a final blitz across Iowa, mindful that the winning margin in the 2008 caucus was 10,000 votes out of just 120,000 cast -- a fraction of Iowa's two million registered voters.
"It's very fluid," Representative Michele Bachmann, a long-shot candidate, told CNN. "There's a long way to go. I have a lot of staying power."
"We are going to take America back. That's what this is about. It is a powerful moment in America's history. And you are on the front lines," Texas Governor Rick Perry, who also lags in the polls, told volunteers.
Iowa -- where unemployment is well below the national average -- is also an unreliable predictor of presidential fortunes: Senator John McCain, the eventual nominee in 2008, came in fourth that year.
Obama, running unopposed for the Democratic nomination, was to address party activists in Iowa by video conference from a posh hotel near the White House and then take his economic message Wednesday to the vital state of Ohio.
Spokesman Jay Carney said the president would say he will "do whatever he can ... to grow the economy and create jobs, to help protect the middle class and expand it."
Former US envoy to China Jon Huntsman skipped Iowa in favor of focusing on New Hampshire, where Romney enjoys a considerable lead.