LE MARS, 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 that’s where the clarity ends in this unpredictable nomination race.

Five others are fighting, as they have all year, to emerge as the Romney alternative.

The ascendant Rick Santorum and Rick Perry are battling to win over social conservatives. Libertarian-leaning Ron Paul is working to preserve support that’s starting to slip. Newt Gingrich is struggling to end his sharp slide. Michele Bachmann is hardly a factor.

“It may be Romney’s to lose at this point,” said John Stineman, an Iowa GOP campaign strategist. “And it’s a battle among the rest.”

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

Paul, who surged last month, has faded some after attacks on his foreign policy positions. 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.

Despite rapidly shifting dynamics, two things were clear on the final weekend before the caucuses: The yearlong effort to establish a consensus 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. The Des Moines Register, which has endorsed Romney, was releasing its final poll before the caucuses Saturday.

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 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 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, including supporter Alan Lucken, who shouted to the candidate: “You’re going to win.”

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.

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.

“I think the world of Rick Santorum. He’s got a great family. But we’ve got some real difference when it comes to fiscal issues,” Perry told supporters in Boone. “Those differences couldn’t be clearer when it comes to important issues in this election like spending.”

Santorum, in turn, charged Perry with hypocrisy: “He had a paid lobbyist in Washington looking for earmarks.”

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.