Mitt Romney narrowly leads rival Ron Paul in Iowa three days before the state kicks off the Republican Party's presidential nominating race, according to a Des Moines Register poll released on Saturday.

The closely watched poll, with a strong track record in Iowa races, showed Rick Santorum surging past Newt Gingrich into third place in a fluid race where 41 percent of likely caucus-goers said they could still change their minds.

The newspaper's poll, conducted Tuesday through Friday, showed Romney with 24 percent support, Paul with 22 percent, Santorum with 15 percent, and Gingrich 12 percent. In fifth place was Rick Perry with 11 percent, and in sixth place was Michele Bachmann with 7 percent.

The poll was released as candidates launched the final stretch run for Tuesday's contest in Iowa, the first in the state-by-state battle to choose a Republican challenger to President Barack Obama, a Democrat, in the November election.

The results were a huge boost to Romney, who has resumed his front-runner's role in the Republican presidential race in the last few weeks after the slide of Gingrich.

A victory for Romney in Iowa, combined with a win in the next contest on Jan. 10 in New Hampshire, could put the former Massachusetts governor on a path to clinching the Republican nomination early.

But Santorum was the candidate with the momentum. The Register poll was taken over a four-day period, and the newspaper said that in the final two days of that period, Santorum was in second place with 21 percent. Romney stayed the same at 24 percent.

The poll was more bad news for Gingrich, the former U.S. House of Representatives speaker who led the race a few weeks ago, but has faded under an onslaught of attack ads from Paul and an outside group that backs Romney.

At a stop in Iowa on Saturday, Gingrich said he would adjust his campaign strategy to respond more forcefully to the attacks.

'Nastier and Dishonest'

We're learning a lot about what our opponents will do. They are nastier and more dishonest than I expected. So we'll have to make some adjustments, Gingrich said in Atlantic, Iowa.

But Gingrich said he would not respond directly to negative ads run by the group that supports Romney.

We may go to a much more clearer contrast, but we're not going to respond in kind, Gingrich said. Those ads are dishonest, and he knows it. They are factually false, and he knows it. And we're not doing anything like that.

The candidates rolled across Iowa in buses on Saturday, stopping at coffee shops, restaurants, and even a car museum to try to win over doubters and energize supporters to turn out to the caucuses.

In Iowa's quirky caucus system, voters gather to cast ballots in public meetings after listening to pitches on behalf of the candidates.

Known for his libertarian views, Paul is taking the holiday weekend off in Texas before returning to Iowa on Monday.

Santorum, a former U.S. senator from Pennsylvania with a strong social-conservative message, is trying to unite Iowa's influential evangelical Christian voters behind him and score an upset with a surge in the final days.

If you really want to transform America, it has to be about values, faith, and freedom, he told a crowd in Knoxville, Iowa.

Gingrich, along with Santorum, Bachmann, and Jon Huntsman, also joined a lawsuit already filed by Perry against Virginia's Board of Elections to qualify for the state's 2012 primary election.

Romney and Paul were the only candidates who managed to submit the required 10,000 verifiable signatures collected by registered voters in the state to get on Virginia's ballot for its March 6 primary.

(Additional reporting by Ros Krasny and Michelle Nichols in New Hampshire, Jeff Mason, Jane Sutton and Lindsay Claiborn in Iowa, and Laura MacInnis in Hawaii; Editing by Bill Trott)