Republican candidates criss-crossed Iowa making late appeals to voters, with polls giving at least three - Mitt Romney, Rick Santorum and Ron Paul - a shot at winning the first contest of the 2012 presidential campaign on Tuesday.
Iowa's quirky caucuses are known more for weeding out candidates than picking the future president. Finishing in a top spot could provide a big boost to any contender in the volatile contest to choose a Republican challenger to Democratic President Barack Obama in the November 6 election.
The tight Republican race, marked by rollercoaster ups and downs in opinion polls for most candidates, has sparked weeks of negative campaigning in Iowa. Millions of dollars has been spent by outside Super PAC fundraising groups.
Former House of Representatives Speaker Newt Gingrich, a one-time front-runner pummelled by such attack advertisements, lashed out at Romney on Tuesday for trying to distance himself from the ads. Asked if he was calling Romney a liar, Gingrich said, Yes on CBS' The Early Show.
This is a man whose staff created the PAC, his millionaire friends fund the PAC, he pretends he has nothing to do with the PAC. It's baloney, said Gingrich.
In response, Romney reiterated that his campaign did not coordinate with the Super PAC and told Gingrich to toughen up.
This is a campaign where you need to have broader shoulders, Romney said on Fox News. If you can't stand the heat of this little kitchen, wait for the hell's kitchen that's coming from Barack Obama.
Polls give Romney, a former Massachusetts governor, a narrow lead over social conservative Santorum and libertarian Paul ahead of Tuesday evening's caucuses. But many voters are still undecided, leaving the contest up for grabs.
More than 100,000 voters will gather across the midwestern state at more than 800 schools, libraries and other public spots starting at 7 p.m. CST (0100 GMT). Results should begin coming in within a few hours.
The weather was expected to be fairly cold, but dry, which should boost turnout. Ice or snow would prompt some voters to avoid the long caucus meetings.
I'm kind of on the fence. A name that's been kind of sticking out, along with everyone, is Rick Santorum. We're not a hundred percent for sure yet, Des Moines resident Jason Harpineau said, just hours before the start of the caucuses.
The stakes are high. A strong performance in Iowa would provide momentum and a surge in donations to the winner or winners - a strong possibility given there is not much breathing space among the three front runners. Ahead is what is expected to be the most expensive election in history.
Romney is aiming for a win that could ease persistent doubts among conservatives about his relatively moderate past stances and propel him toward clinching the nomination early. He is heavily favoured to win next week's New Hampshire primary.
Santorum, a former U.S. senator from Pennsylvania, hopes positions such as his staunch opposition to gay marriage will consolidate Iowa's influential religious right to emerge from Iowa as the latest conservative alternative to Romney.
A win by Paul would help the Texas congressman extend his minimal-government stance and broaden the appeal of his campaign outside his zealous base, many of them young voters.
Struggling rivals like Texas Governor Rick Perry and U.S. Representative Michele Bachmann are fighting for at least a fourth-place finish that could preserve their flickering hopes.
Gingrich, who led the race just weeks ago, aims to end his slide and prove he can make another comeback.
MOMENTUM AND ELECTABILITY
Romney's Iowa campaign chairman, Brian Kennedy, said he thought a higher turnout would bode well for Romney because he draws support from a broad swath of the party.
We're in a strong position but the unique thing about caucuses is you never really know, Kennedy said. If he does well, it will give him a lot of momentum going to New Hampshire, South Carolina and Florida.
Surveys show Romney performs best of all the Republicans in head-to-head matchups with Obama in a general election campaign certain to focus on the economy and high unemployment.
The caucuses start a frenzied month for the Republican presidential hopefuls that will include a half-dozen debates in January and three more state votes -- on January 10 in New Hampshire, January 21 in South Carolina and January 31 in Florida.
Gingrich dropped in Iowa polls after attacks from Paul and the Super PAC backing Romney. Gingrich's jab at Romney in the intense contest's last hours was a sharp contrast with his promises to stick to a positive message.
I would simply ask you go to the caucus tonight, and say to your friends and neighbours, that Iowa has a remarkable opportunity to say no to every candidate that has been running negative ads, Gingrich urged supporters in Burlington, Iowa.
Iowa's nominating contest has traditionally cleared the field of losers and elevated surprise contenders. Former Arkansas Governor Mike Huckabee won the 2008 Republican caucuses. The eventual nominee, Arizona Senator John McCain, finished fourth.
Obama launched his White House run with an Iowa win four years ago. This time, Obama is the only Democrat running, but the party is holding caucuses anyway and he will address caucus-goers by video on Tuesday night.
Marcia Brom Smith, a Democrat and U.S. Navy veteran, attended a Romney rally in Des Moines to see if she would consider voting for him instead of Obama in the general election, but was not yet convinced.
I liked some of what he said. I don't think Obama should be blamed for the bad economy. The Congress is partly to blame in my view, she said. I did like what he (Romney) had to say about getting back to American values.
(Additional reporting by Eric Johnson, John Whitesides and Lindsay Claiborn in Iowa; Writing by Patricia Zengerle; Editing by Vicki Allen)