Appearing on several Sunday news programs, Mr. Paul waved aside the finding of a poll by the Des Moines Register that suggested nearly a third of Iowa voters believe he would be the least able to defeat President Obama in the general election.
"Maybe it's not true," Mr. Paul said on CNN's "State of the Union" program. "I've been pretty electable. I was elected 12 times once people got to know me in my own congressional district. So I think that might be more propaganda than anything else."
Appearing on CBS's "Face the Nation," Mr. Paul's son, Rand Paul, a senator from Kentucky, assailed Mr. Santorum as a "big government type of moderate" who will not fare well as people learn more about his record.
"A lot of people don't know that because he hasn't surged to the top yet so he hasn't had much scrutiny," Rand Paul said on the program. "When he has the scrutiny, I think he's going to have some of the same problems that some of the other fair-weather conservatives have had."
Mr. Santorum, whose support has tripled in the Register poll, predicted that his campaign would emerge from Iowa with "a big jump" and said it was because the voters want someone who can defeat the president in the fall.
"The people of Iowa, the more they look, the more they are going to see the person who is exactly the right person," Mr. Santorum said on NBC's "Meet the Press." He said that if his campaign could do better tha Representative Michele Bachmann and Gov. Rick Perry of Texas, "we'd be in good shape, and we're moving towards that right now."
Asked about his endorsement of Mr. Romney during the 2008 presidential campaign, Mr. Santorum said he did so as a way of opposing Senator John McCain of Arizona, not because he believed strongly in Mr Romney.
"I made the political judgment – right or wrong – that he had the best chance to stop John McCain," Mr. Santorum said.
The last-minute television interviews came as the candidates began their final sprint to the finish line in Iowa, where a cold blast of air pushed out the unseasonably warm temperatures. A brief blizzard in western Iowa on New Year's Eve was a reminder of how campaigning for president usually takes place here.
Mr. Paul remained in Texas with plans to return to Iowa on Monday, and Jon M. Huntsman Jr. -- who is not competing in Iowa -- remained in New Hampshire, waiting for the media blitz to arrive on his doorstep on Wednesday.
But the rest of the candidates began the first day of 2012 back in their buses. Mrs. Bachmann started the day at a church event; Newt Gingrich planned several meet-and-greet events in Ames and Marshalltown; Mr. Romney set off for events in Atlantic and Council Bluffs; Mr. Santorum was scheduled to have three events in western Iowa.
Mrs. Bachmann, whose campaign has plunged into last place, sought to portray the recent polls as lagging indicators and insisted that she will be the beneficiary of an undetected surge of support among conservatives in the state.
"Polls sometimes belie the truth on the ground, and that's what we see," she said on ABC's "This Week" program "This is a 50-state race. And we intend to participate not only in New Hampshire, South Carolina, Florida, but to go all the way, because I intend to be the Republican nominee and defeat Barack Obama in 2012."
Mr. Gingrich attended mass at St. Ambrose Cathedral in Des Moines Sunday morning, and told reporters afterward that Mr. Romney's campaign will spend enormous amounts of money to defeat his Republican rivals. Mr. Gingrich has been the target of millions of dollars of attack ads, much of it paid for by Super PACs supporting Mr. Romney.
"Romney would buy the election if he could," Mr. Gingrich said.
Mr. Romney did not appear on any news programs on Sunday morning. But he prepared to begin another bus trip across the state as his campaign reveled in the results of the Register poll, which showed him statistically tied with Mr. Paul for the lead here.
