Whether the caucuses will actually winnow the field, though, is anyone's guess.
Several polls indicate a tight race among three candidates -- U.S. Rep. Ron Paul, former Massachusetts Gov. Mitt Romney and former House Speaker Newt Gingrich, with former U.S. Sen. Rick Santorum creeping up on the outside. But the rest of the field is so close that one slip could create an opening wide enough for Rep. Michele Bachmann of Minnesota or Texas Gov. Perry to slip through.
A Public Policy Polling survey last week indicated Paul ahead of Romney and Gingrich, with Bachmann, Perry and Santorum nipping at Gingrich's heels, turning Iowa into a likely two-person race between Paul and Romney.
If Paul can get young people and independents who don't usually vote in Republican caucuses to turn out Tuesday, he'll win, PPP said. If turnout has a more traditional look, Romney likely will prevail. But with this year being anything but normal, Santorum could be the sleeper, despite Bachmann devoting endless time in her home state. (For his part, Santorum said he would drop out of the race if he makes a poor showing in Iowa.)
The New York Times projected Paul would capture 25.6 percent of the vote, with a 60 percent chance of winning the caucuses. Romney was second with 21.5 percent of the vote and a 31 percent likelihood of winning. With a projected 13.7 percent of the vote, Gingrich was third with a 4 percent chance of winning.
The Times said its forecasts were developed from an average of recent surveys, adjusted for a polling firm's accuracy, the freshness of a poll and each candidate's momentum.
RealClearPolitics.com's polling average indicates Paul will wear the winner's mantle on Tuesday, albeit by a slim margin.
And less than a week before the caucuses, Rasmussen Reports said its survey indicated an unnamed Republican would best Obama in November by a statistically insignificant 1 percentage point, 45 percent to 44 percent, indicating Republicans still aren't excited about any of the candidates yet.
This year's campaign is unusual because the GOP race -- with its ever-changing front-runners and surges -- has given all candidates some degree of hope of remaining in the race after Tuesday.
But here's another credible scenario: With more scrutiny being paid to Paul's record on race, Gingrich's surge fading, and Bachmann, Perry and Santorum splitting the evangelical vote, Romney could win.
As nearly all major candidates -- former Utah Gov. Jon Huntsman is banking on success in New Hampshire's primary over Iowa's caucuses -- crisscrossed the Hawkeye State in the run-up to the caucuses, the real focus was on Romney, Gingrich and Paul, The Washington Post reported.
The prospect of a Romney victory in Iowa has sounded the alarm for almost every other candidate in the Republican field, observers say. Iowa is considered a difficult state for Romney because of the heavily conservative bent of many activists. Should he win Tuesday, and clean house next week as expected in New Hampshire, Romney would have a tremendous edge to win the GOP nod.
Romney sounded confident about his overall prospects, telling the Post recently, "I think I'm going to get the nomination if we do our job right."
One political analyst told The Hill Romney could sew up the GOP nomination quickly because he's seen as all-but unbeatable in New Hampshire's Jan. 10 primary.
"If he comes in first or second in Iowa and wins New Hampshire, he will be the prohibitive favorite. It's very difficult to see a scenario where he's not our nominee," said Al Cardenas, head of the American Conservative Union, who is officially neutral in the 2012 contest but worked on Romney's 2008 campaign.
Gingrich hoped to regain some of the momentum he had before his star began to fade amid negative ads aimed at him in recent weeks. His campaign also hoped to counter the growing impression Romney was positioned to win in Iowa.
Even as Romney and Gingrich watch out for the other, both must keep an eye on Paul, the libertarian conservative whose organizational skill and enthusiastic base put him in the thick of the battle.
Still, state party officials say they're amazed at how unsettled the field remained with less than a week to go.
"It's completely unprecedented to have a field and a cycle that has been this unpredictable, this turbulent late in the process," Iowa Republican Party Chairman Matt Strawn told CNN.
Tim Albrecht, spokesman for Iowa Gov. Terry Branstad, also expressed surprised.
"I have never seen this level of undecided voters this late in the process," Albrecht said. "It's a crazy year in that regard."
Iowa's Republican Party apparently decided to move the counting of returns in Tuesday's caucuses from the state party headquarters in Des Moines to a secret location because of security concerns, several media outlets reported.
State party officials have refused to confirm the decision that was prompted by threats from some Occupy the Caucuses protesters to disrupt campaign events, CNN said. So far, Occupy organizers said they weren't planning on any disruptions, but GOP officials said they were preparing just in case.
In a statement, Strawn didn't comment specifically on steps he is taking, saying only considered actions are being implemented to safeguard security.
"The Iowa GOP is taking additional safeguards to ensure the caucus results are tabulated and reported to the public in an accurate and timely manner," Strawn said.