Des Moines, Iowa ? With time running short, Ron Paul, Rick Santorum and other Republican presidential contenders insisted they could beat President Barack Obama as they worked to persuade undecided Iowa Republicans aching to win the White House to choose them over chief rival Mitt Romney.

“I’m the candidate that actually was able to win in states, as a conservative, in getting Democrats and independents to vote for us,” Santorum, the former Pennsylvania senator who is surging in the race and is a favorite among cultural conservatives, said in an interview on CNN. “Mitt Romney has no track history of doing that.”

Paul, a libertarian-leaning Texas congressman who Romney has said is outside the GOP mainstream, countered the suggestion that he’s a fringe candidate. In an interview with ABC from his home state, where he was spending the weekend, Paul insisted: “I’m electable. I’ve been elected 12 times in Texas, when people get to know me.”

With Romney in a position of strength in Iowa, both Santorum and Paul went directly at the former Massachusetts governor’s chief argument — that he is the most electable Republican in a head-to-head matchup against Obama next fall. They hope they can sway the roughly half of likely caucus-goers who say they are undecided or willing to change their minds two days before the leadoff presidential caucuses.

A Des Moines Register poll released Saturday showed Romney and Paul locked in a close race, with Santorum rising swiftly to challenge them. Nearly half of likely Iowa caucus-goers view Romney as the Republican most likely to win the general election. He was far ahead of Santorum and Paul, who was viewed as the least likely to win.

Those two are fighting against the notion in GOP circles that their bases of support are narrow and neither would be able to cobble together the diverse voting coalition necessary to beat Obama in November. Paul attracts legions of backers who put states’ rights above much else, while Santorum — an anti-abortion crusader — is popular among Christian conservatives who make up the base of the Republican Party.

In contrast, Romney has styled himself as a Republican able to attract a broad spectrum of voters. As polls showed him in strong standing in Iowa in the past week, he has redoubled his effort to portray himself as the business-savvy executive with national appeal who is best able to defeat Obama on the campaign’s most pressing issue, the economy.

Although the race remains fluid, it appeared that Romney’s carefully crafted plan to avoid underperforming in Iowa, where he campaigned little until last week, may be working, given a divided GOP electorate torn between several more conservative candidates and Paul’s appeal to libertarians.

The issue of what type of candidate to choose cuts to the heart of why the Iowa race is so volatile; an NBC/Marist poll last week showed nearly even percentages of Iowa caucus-goers want a candidate who shares their values as want a candidate who can beat Obama.

“The first thing you see when you talk to any Iowa Republican is that desire to beat Barack Obama,” Iowa GOP Chairman Matt Strawn said.

Mindful of that, both Romney and Santorum canvassed the state Sunday to make the electability case — and their schedules illuminated their late-game strategies for rallying their backers to the caucuses.