Poll shows Romney leading Iowa, Santorum surging Reporting from Des Moines - Iowa's most influential poll shows that Tuesday's caucuses are Mitt Romney's to lose, but that Rick Santorum may be emerging as a last-minute and powerful threat. The Des Moines Register poll, released Saturday night, shows Romney at 24% among likely Republican caucus participants, with Ron Paul right behind him at 22% and Santorum in third place at 15%. The poll was conducted over four days this week, but according to the survey, by pollster Ann Setzer, Santorum surged to 21% over the final two days of polling, suggesting that voters have gravitated to him as his media profile has risen. Santorum had long set his sights on Iowa, traveling tirelessly throughout its 99 counties and giving hundreds of events, and until this week he had shown little in terms of viability. As support for Newt Gingrich has fallen off, however, no one has benefited more than Santorum. The poll also suggested Santorum was siphoning support away from Paul. Over the final two days of polling, Paul dropped to 18% while Romney remained at 24%. Santorum has taken to bashing Paul's foreign policy outlook repeatedly, warning about the threat posed should Iran obtain a nuclear weapon. The poll has Gingrich down to 12%, with Rick Perry right behind him at 11%. The fast-fading Michele Bachmann was at 7%. As an indicator of the race's ongoing volatility, 41% of caucus-goers interviewed said they could still change their minds. The results will be welcome news for the Romney campaign, which slowly has invested more and more resources in the state. The GOP front-runner campaigned here again Saturday. Should Romney pair a win in Iowa with an expected victory Jan. 10 in New Hampshire, he could be in a commanding position to capture the Republican nomination. But his campaign won't be able to ignore Santorum's rise, as it's likely is fueled by support from evangelical voters, many of whom have shown little interest in backing Romney. A strong Iowa showing could give Santorum, a former two-term Pennsylvania senator, a springboard to compete in South Carolina, with its strong base of social conservative voters, and Florida. Setzer is best known for accurately predicting Barack Obama's surprise upset of Hillary Rodham Clinton in Iowa four years ago. Selzer & Co. of Des Moines conducted the survey of 602 likely GOP caucus participants, which has a margin of sampling error of plus or minus 4 percentage points. In the final two days of polling, 302 likely caucus-goers were screened, with a margin of error of plus or minus 5.6 percentage points.