(Bloomberg News) His rivals crisscross Iowa in campaign buses wired for satellite television with their faces painted on the sides. They have spent millions on advertising. Rick Santorum has trudged along in a pickup truck driven by a lone supporter. He has a minimal presence on television.

And he may be positioned to deliver the biggest surprise of the Republican presidential race.

The former U.S. senator from Pennsylvania, now in third place in the most closely watched Iowa poll, has spent more time in the state than any opponent, traveling to all 99 counties over more than 100 days. He's trying to validate the campaign axiom of the Iowa caucuses: organize, organize, organize and get hot at the end.

"This is an election that will be very close," Santorum told a group gathered yesterday in a crowded coffee shop in Sioux City, Iowa. "Our support is rallying and rising here, but there's two more days and there's a lot of work to be done."

In a year when social conservatives have bounced among candidates, Santorum's timing in Iowa could be spot on if he can manage to consolidate their votes in the way former Arkansas Governor Mike Huckabee managed to do in 2008.

U.S. Representative Michele Bachmann of Minnesota, Texas Governor Rick Perry and former U.S. House Speaker Newt Gingrich of Georgia have also tried to court social conservatives as they present themselves as an alternative to former Massachusetts Governor Mitt Romney. None has managed to do so.

Iowa Poll Results

A Des Moines Register Iowa Poll released Dec. 31 showed Santorum backed by 15 percent of likely Republican caucus-goers, after a surge in the final two days of sampling. Ahead of him were Romney, at 24 percent, and U.S. Representative Ron Paul of Texas at 22 percent.

Late last month, Santorum won the personal endorsement of Bob Vander Plaats, a former candidate for Iowa governor and the president of the Family Leader, a coalition of social conservatives in the state.

How much that endorsement has helped him is hard to know, especially since it appears social conservatives may play a smaller role in this year's Iowa caucuses than four years ago.

In 2008, exit polls showed 60 percent of those who attended the Republican caucuses described themselves as born-again or evangelicals. The Register's Iowa Poll shows that proportion could be closer to one-in-three on Jan. 3.

Modest Crowds

Santorum, 53, has attracted modest crowds at his events in recent days. At a weekend stop at a library, reporters and photographers outnumbered the roughly 50 people who had come to hear Santorum in Indianola, Iowa. Smaller crowds could be the result of how much time Santorum has already spent in the state. He told the Indianola audience that it was his fourth or fifth visit to the city so far in the campaign.

Joseph Vorwald, 56, a group home worker who lives there, said it was the third time he'd seen Santorum in person.

"His message rings with people," Vorwald said. "I think social conservatives will come to him because he's walked the walk and fought partial-birth abortion."

Reah Adamson, 62, an insurance company worker who lives in Carlisle, Iowa, said she plans to back Santorum. She said that's easier to do now that he's showing polling movement.

"If you're going to caucus for someone, you want to support someone who has a chance," she said.

Adamson, who came out to see Santorum this weekend before finally deciding to back him, said she is not concerned about his electability in a general election.

"I don't think it's going to matter that much," she said. "I think any of the candidates are electable."

Final Hours

As he races through the final hours before the caucuses, Santorum is telling voters to trust their own judgment and not listen to others.

"You recommend to the nation who you believe, not what the pollsters believe, not what the pundits believe, but who you believe having researched and questioned these candidates more than any other group of America will," he said in Sioux City yesterday. "You suggest who you think the best person is to lead this country."

Santorum also is making what could be construed as a criticism of Romney, who Republicans have yet to rally around because some fear he's not conservative enough.

"Don't settle for less than what this country needs," he said in Indianola on Dec. 31, adding that it might not be a real victory if the person who wins the nomination "may not do what's necessary to make the changes that we need."

As Santorum has edged higher in polls, he has drawn challenges from his rivals, especially Perry.

'Real Differences'

During a Dec. 31 stop at a restaurant and sports bar in Boone, Iowa, Perry said there were "real differences" between the two men on fiscal issues.

He specifically cited Santorum's repeated votes to raise the federal debt ceiling while in the Senate and his use of earmarks for projects in Pennsylvania, which Perry said presented a "fleecing" of taxpayers.

In a Dec. 29 Fox News interview, Santorum defended his use of earmarks while in Congress.

"I'm proud of the money that I did set aside for things that were priorities in my state," he said.

Unlike Romney and Paul, who have flooded Iowa's airwaves with commercials, Santorum has spent relatively little on advertising.

"I know all the campaigns say they need your help," he said in Indianola. "They're lying. I need your help. I'm not the one running two or three or five million dollars worth of television."

Fundraising Pickup

In a brief Dec. 31 interview, Santorum said his fundraising has picked up a "little bit" since his polling uptick.

"We're able to start running ads in New Hampshire and South Carolina and hopefully things will pick up as, you know, we see what happens on Tuesday and obviously that will be the real determinant," he said.

Asked if a third-place finish in Iowa would be good enough to make him a more significant factor in the nomination race, he said: "I think it will be a great thing."

In Sioux City yesterday, Santorum took a swipe at Paul, saying he and Obama share a similar foreign policy. Paul has called for a dramatic reduction of U.S. military forces outside the country's borders.

"I predict that if President Obama has four years where he's not looking to re-election, his foreign policy will not be any different than Ron Paul's foreign policy," he said.

Conservative Views

Doris Ung, 55, said that after initially thinking about supporting Gingrich, she's now behind Santorum because of his conservative views and position on foreign policy.

"I always had a sense that I might go that direction but I had to be convinced," said Ung, who lives in Sioux City.

She said she saw him speak at her church and was impressed with his drive to fight partial birth abortions.

"I feel like he has the ability to continue pushing through," she said.

Santorum is also appealing to the self interest of Iowans who want to keep their first-in-the-nation caucus tradition alive in subsequent elections by suggesting that the candidate who spends the most time on the ground should be rewarded.

"If that's what you want for future Iowa caucuses, then come out and show what Iowa is all about," he said in Indianola.