Republican Rick Perry (back to camera) greets supporters during a Dec. 27 campaign stop at the Main Street Cafe in Council Bluffs, Iowa.
Former Sen. Rick Santorum dons a National Rifle Association hat while talking to reporters at Doc's Hunt Club in Adel, Iowa, on Dec. 26.
Former House Speaker Newt Gingrich and his wife, Callista, walk off his campaign bus during a Dec. 27 stop at the Dubuque Golf and Country Club in Dubuque, Iowa.
Rep. Michele Bachmann speaks during a campaign stop at King's Crossing Cafe in Mondamin, Iowa, on Dec. 27.
Mitt Romney speaking at the Hotel Blackhawk in Davenport, Iowa on Dec.27.
A campaign sign for Republican presidential candidate U.S. Rep. Ron Paul of Texas sits at an intersection in Ankeny, Iowa on Dec. 27.
1 of 6
In this final week before the Iowa caucuses on Jan. 3, each of the Republican presidential candidates is starting an all-out scramble to shore up support in a contest that's still up for grabs.
Former House Speaker Newt Gingrich and former Massachusetts Gov. Mitt Romney are competing for the votes of moderate, mainstream Republicans. Both of them have spent time at the top of the polls.
Texas Gov. Rick Perry, Rep. Michele Bachmann and former Sen. Rick Santorum are focused on capturing the evangelical voters who fueled the surprising 2008 victory of former Arkansas Gov. Mike Huckabee. Conservative Christian voters make up roughly more than half of caucus voters, but polls this year have shown they haven't coalesced behind a single candidate, as they did in 2008.
Former Utah Gov. Jon Huntsman is not competing in Iowa, instead staking his chances on the next primary, Jan. 10, in New Hampshire.
And then there's Rep. Ron Paul of Texas, who has vaulted to the front of the pack off of a strong grassroots campaign without relying heavily on mainstream GOP or evangelical support.
Here's what each candidate needs to do this week to gain an edge:
Ron Paul: The Texas congressman is beginning to see more benefits of the strong volunteer organization he has built — particularly after an Iowa State/Gazette/KCRG poll Dec. 18 showed him having surpassed Newt Gingrich and Mitt Romney as the leader, at 28 percent. (Other polls show Paul with a narrower lead, or trailing Romney.) Paul lacks support among Republican Party mainstreamers, but his message of civil liberties has drawn an enthusiastic coalition of young people and libertarian-leaning voters.
His challenge over the next week will be to get his supporters out to vote. (A large number of them are college students — some from out of state — who will still be on winter break on Jan. 3.) Paul may also face lingering questions about controversial newsletters published in the 1990s.
"Pretty much everybody here recognizes he's got ... no doubt the most enthusiastic following," says University of Iowa political science professor Tim Hagle. "He'll probably finish about second. If turnout is low, it could help him win."
Newt Gingrich: The former House speaker appears to be losing momentum at precisely the wrong time, and may lack the field organization to hold his support in place. He'd been the front-runner over the last month until the Iowa State/Gazette/KCRG poll showed him supplanted by Paul. His slide coincides with an onslaught of attack ads questioning his conservative bona fides. (His campaign on Tuesday had to defend his previous support of reforms brought by the health-care legislation that Romney signed into law when he was governor of Massachusetts.)
Gingrich hasn't had the kind of solid ground forces that could capitalize on his surge in the polls. In recent days he has tried to lower expectations, saying that he'd be satisfied with a third- or fourth-place finish. His campaign's decision to eliminate half of the planned 44 stops on a bus tour this week could be another sign that his campaign could fizzle Jan. 3.
"This follows a pattern of him not delivering on things that he's planned for," Hagle says. "I'm wondering if some caucus-goers might find that troubling. He's trending down fast."
Mitt Romney: He has hovered at or near the top of the polls for months but has been unable to gain much more than 25 percent, as the party cycles through its "Anybody But Mitt" choices. Among Iowans, conservatives question his conservative credentials and some evangelicals are suspicious of his religious faith as a Mormon.
Since he lost to a more conservative candidate — Huckabee — in 2008, Romney decided from the start not to invest too much effort in the state and hasn't spent as much time there as his opponents.
Instead, Romney has staked his candidacy on winning New Hampshire. But in recent days, with polls showing him gaining some ground there —the Rasmussen poll released Dec. 21 actually shows him in the lead — there are signs he could finish stronger than he first expected.
Romney still has an organization in Iowa and solid support held over from his 2008 presidential bid, when he finished second. And unlike the other hopefuls, Romney already has both a national organization and name recognition.
"He doesn't need to win Iowa. He just has to make sure Gingrich doesn't win Iowa," Hagle says.
Still, many believe he's well-positioned take second or win outright.
Rick Perry: After a strong start in the polls — he was the front-runner for a time back in August — Perry's embarrassing debate performances have pushed him to the middle of the field.
He's using his deep campaign pockets to blanket Iowa with TV ads that some say appear to resonating locally, particularly among previously undecided voters. The ads have introduced him to Iowans and hit hard against his opponents, portraying him as the only true Washington outsider in the race.
His presence on air has allowed him to maintain a polling edge against the financially strapped campaigns of Rep. Michele Bachmann and former Sen. Rick Santorum, his two main competitors for conservative voters.
This week he has restarted his bus tour and brought along Louisiana Gov. Bobby Jindal on some stops.
"The TV camera shows he's a warm guy. And he's very good in the town halls. He needs to do more of that to shore up the advertising he's done," Hagle says. "There's a chance he could do well."
Michele Bachmann: Since winning the Ames Straw Poll, Bachmann, who touts her Iowa birth and a legion of Tea Party support, has been eclipsed by her opponents. Along the way, the Minnesota congresswoman has been unable to expand beyond the ardent support of the hardcore conservative voters.
That, observers say, is her biggest problem: she's too conservative to win a general election, and Iowans know it. Since October, she has hovered at or below 10 percent in most polls.
As she continues her own bus tour this week, Bachmann is hoping to solidify the enthusiasm that surrounded her campaign launch in Iowa in June.
"I think a lot of her organization is still there. At this point, it's a matter of trying to hang on to her supporters and try to gain some new ones," Hagle says. "But she doesn't have a lot of resources and can't get on TV much."
Rick Santorum: The former senator from Pennsylvania, a staunch opponent of abortion and a devout Catholic, would seem the ideal candidate for an electorate that has moved solidly to the far right. But despite billing himself as the race's "only true conservative" — and becoming the first candidate to visit all 99 counties — he remains at the bottom of the polls.
Yet his shoe-leather approach has many observers thinking Santorum could finish stronger than expected. He has drawn progressively larger crowds at his stops. And last week his campaign announced the endorsements of Sioux City conservative talk-radio host Sam Clovis and Bob Vander Plaats, who heads the conservative group Family Leader.
Santorum also has the support of Iowa's secretary of state and several well-known pastors. The support of ministers could be pivotal because they tend to influence the voting habits of their congregants.
"The time that he's put in and the enthusiasm of his supporters tell me he might do well on caucus night and surprise some folks," Hagle says. "All of that work isn't showing up in the polls, but that kind of work didn't show up ahead of time for Huckabee [in 2008] either."