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 both inside and outside the candidates' campaigns suggest that Romney is in strong contention to win Tuesday's caucuses.
Paul, who surged this month, has faded some following 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 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 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. 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 percent while Paul had 22 percent. Santorum was third with 15 percent of likely voters backing him.
Gingrich had 12 percent support and Perry had 11 percent. Bachmann trailed with 7 percent.
But the poll showed Santorum ascendant and Paul falling. During the last two days of the poll, taken Dec. 27-30, Santorum drew 21 percent while Paul had fallen back to 18. The survey showed that 41 percent of likely caucusgoers say they still might change their minds.
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."
"I'm planning on it," Romney said and later told a reporter, "I sure hope to. I'll tell you that."
In another show of confidence, Romney promised to return to Iowa, a perennial general election battleground, if he is the nominee.
