DES MOINES, Iowa - Mitt Romney is the clear Republican front-runner in Iowa in the final days before the first voting in the 2012 presidential election, but polls also suggest large numbers of Republicans could change their minds before Tuesday's caucuses.

Five other candidates are fighting, as they have all year, to emerge as the conservative alternative to Romney, the former Massachusetts governor, in the state-by-state nominating contests to pick a challenger to Democratic President Barack Obama in November's election.

Polls show Obama is vulnerable as he seeks a second term, weighed down with voter dissatisfaction over his handling of the economy and the stagnant recovery from the recession.

Only three or four candidates typically make it out of Iowa with enough momentum and money to continue in the race.

The ascendant Rick Santorum, the former Pennsylvania senator, and Texas Gov. Rick Perry are battling to win over social conservatives. Libertarian-leaning Texas Rep. Ron Paul is working to preserve support that's starting to slip. Former House Speaker Newt Gingrich is struggling to end his sharp slide. Minnesota Rep. Michele Bachmann is hardly a factor.

"It may be Romney's to lose at this point," said John Stineman, an Iowa Republican campaign strategist who has been monitoring internal and public polls. "And it's a battle among the rest."

Although much can happen before Tuesday's caucuses, public surveys and internal polls as well as interviews with Republican activists, Iowa voters and political operatives both inside and outside the candidates' campaigns suggest that Romney is in strong contention to win in Iowa.

A new poll by The Des Moines Register, which has endorsed Romney, late Saturday showed Romney and Paul statistically even at the front of the pack. Romney had 24 per cent and Paul had 22 per cent. Santorum was third with 15 per cent of likely voters backing him.

Gingrich had 12 per cent support and Perry had 11 per cent. Bachmann trailed with 7 per cent

Paul, who surged this month, has faded some following attacks on his foreign policy positions as being outside the Republican mainstream. Paul opposes intervening militarily to prevent Iran from acquiring nuclear weapons, advocates withdrawing U.S. troops from Afghanistan, and wants to end U.S. aid to Israel and other allies.

Santorum and Perry are climbing, but evangelical Republicans and cultural conservatives continue to divide their support among the field -- giving Romney an opening. And a large contingent of voters hasn't yet locked in on a candidate as the clock winds down.

Despite rapidly shifting dynamics, two things were clear on the final weekend before the caucuses: The yearlong effort to establish a consensus conservative challenger to Romney had failed, and Romney's carefully laid plan to survive Iowa was succeeding. It relies on conservative voters failing to rally behind one candidate.

He was either slightly ahead or in a virtual tie with Paul in NBC/Marist and CNN/Time polls, with Santorum running third.

With the stakes high, the candidates pressed their closing messages Saturday and released final TV ads while volunteers and staffers canvassed the state to both persuade the undecided and mobilize backers.

Notably absent was Paul, the Texas congressman who returned to his home state late Friday. He had no campaign events in Iowa until Monday; his campaign said he was spending the holiday weekend with his family. Paul, however, is appearing on several Sunday morning television news programs.

By Saturday afternoon, an upbeat Romney had returned to Iowa from a brief trip to New Hampshire. In Le Mars, he drew a crowd of 300 people.

He spent the afternoon in conservative Plymouth County and more populous Woodbury County, both winning areas for him during the 2008 race. He finished second in the state that year behind former Arkansas Gov. Mike Huckabee, a Baptist minister who enjoyed strong support among evangelicals, although Arizona Sen. John McCain later captured the party's nomination.

Romney planned to campaign Monday in cities he won four years ago -- Cedar Rapids, Davenport and Dubuque. He wants to maximize the edge he holds in critical areas rather than risk underperforming in places where more ardent conservatives are leery of his Mormon faith and shifting positions on social issues such as abortion and gay rights.

Santorum, meanwhile, looked to capitalize on his recent surge in polls by focusing on southern portions of rural Iowa, where the former Pennsylvania senator has made a point of visiting more often than his rivals. And he rolled out a new TV ad casting him as "a trusted conservative who gives us the best chance to take back America."

Perry's advisers see Santorum within reach and have begun attacking the former senator for having supported spending on home-state pet projects, an unpopular position in these tough economic times. Santorum, in turn, charged Perry with hypocrisy, saying the Texas governor had a lobbyist in Washington to seek federal money for projects in his state.

Perry has seen his fortunes improve some in recent days in part because he and his allies have advertised the most aggressively. Of the more than $3 million in television ads he has spent, the final round included spots promoting him as a Washington outsider, and Santorum, Bachmann, Gingrich and Paul as insiders.

Gingrich, for his part, was spending the weekend pleading anew with Iowans to side with him despite what they have learned about him through millions of dollars in attack advertising by Paul and a political action committee bankrolled by Romney supporters.

"Iowa could actually dramatically change people's understanding of what works in politics if you repudiate that kind of negativity," Gingrich told 150 people at a Council Bluffs restaurant Saturday.

Bachmann, who had fallen since last summer to single digits in Iowa polls, spent the day at her Des Moines-area state campaign headquarters rallying supporters and volunteers.

At least 10 protesters connected to the nationwide Occupy Wall Street movement were arrested outside Bachmann's office in a suburban Des Moines strip mall. Eight more protesters were later arrested on trespassing changes outside the campaign offices of Gingrich and Santorum.

Former Utah Gov. Jon Huntsman, who served as Obama's ambassador to China, is skipping Iowa entirely, pinning all his hopes on a strong showing in New Hampshire, which holds the season's first primary on Jan. 10. Huntsman was attending six New Year's Eve house parties across New Hampshire.