How long can Santorum's meteoric rise last?

Rick Santorum's upstart finish atop the field in Iowa is a scenario no one would have predicted a mere two weeks ago. It was a validation of his faith in both traditional retail politics and the power of the state's Christian conservatives. On Tuesday night, he thanked his wife, God and Iowa, in that order.

For most of this most volatile of election cycles, nobody paid much attention to Santorum, a former Pennsylvania senator who hasn't held office for five years and is best known for his very conservative stands on social issues. He was not the most dynamic or the best-funded candidate in the GOP field. But he was among the most dogged, visiting all 99 counties in Iowa and holding more than 370 town halls across the state.

After a pair of late polls showed Santorum inching up into the top tier, he packed one venue after another, drawing increasingly enthusiastic crowds despite the bitter cold. People jammed into coffee shops, libraries and a bank basement. Some indoor events had to be moved outside to accommodate the throngs. The surging interest carried him to about 25 percent in the caucuses, statistically tied with Mitt Romney and ahead of a third-place finishing Ron Paul.

It's a tie! So Santorum wins
How Rick rolls
Full CBS News coverage of the Santorum campaign

Yet Santorum faces an immediate question even as he celebrates his strong showing in Iowa: Can he duplicate his achievement in other states? Those who know New Hampshire and South Carolina best say that the climb ahead will be steep.

For a start, Santorum's campaign has only five paid staff in New Hampshire and four in South Carolina. And although fundraising has been on the uptick (campaign aides say Santorum has garnered more money in the last week than in the previous six months, although they declined to cite specific numbers), his war chest is paltry compared to Romney's.

Santorum also has demographic obstacles. Culturally conservative evangelical voters made up nearly 60 percent of GOP caucus-goers Tuesday night in Iowa, according to entrance polls. But they constitute a much smaller percentage of Republican voters in New Hampshire, said Andrew Smith, director of the University of New Hampshire's Survey Center. Moreover, the Granite State has traditionally been much friendlier to moderates.

"The kind of voters who Santorum is relying on in Iowa don't exist here, so he's going to have a hard time," said Smith.

In a state the size of South Carolina, the money to run ads and aggressively spread his message will be paramount, said Republican strategist Jim Dyke. But the bigger problem for Santorum, Dyke said, is that his campaign lacks mass appeal.

"He's got a very narrow message which is 'I'm the most conservative candidate.' And I think when we get to South Carolina, the question is going to be one of experience and one of electability, and I don't think he's going to win either," said Dyke, who is neutral in the race.

The candidate and his campaign cede no ground on electability. Santorum entreats audiences to "win with someone we can trust."

John Brabender, Santorum's longtime senior strategist and media consultant, says his boss is "uniquely qualified" to provide the best contrast with Obama. "Our message first and foremost is that we're the strongest opponent" of the president, he said.

However, Santorum's contention that he is more electable than the other candidates is undercut by his 2006 loss to Democrat Bob Casey by an 18-point margin. It was the largest Senate loss in Pennsylvania history and the largest in the country that year, and it was in a state critical to winning the White House.

The Santorum campaign insists that it has been preparing to translate a strong showing in Iowa into equally solid results in New Hampshire, South Carolina and onward, using the same grassroots strategy that they've counted on all along. They say Santorum has held public events in New Hampshire nearly as often as Romney and has been in South Carolina more than any other candidate. They also claim an army of volunteers they say will elevate his ground game.

Santorum has also been trying to demonstrate he is capable of broader appeal, in particular to blue-collar Republicans and "Reagan Democrats." He frequently talks about bolstering manufacturing in the United States and touts his hawkish foreign policy credentials. "He gets pegged as a one-trick pony, but he's not," said Santorum national political director Michael Biundo, who worked with Pat Buchanan in New Hampshire in 1996. "He always says he can walk and chew gum at the same time."

Don't expect Santorum to stop talking about cultural issues -- the signature of his career in politics -- as the race wears on. Over the last few days, Santorum has unapologetically promoted marriage as an antidote to poverty, railed against the idea of diversity as an American value and advocated a return to biblical principles in public life. His passionate anti-abortion views and opposition to gay marriage, as well as his emphasis on his Christian faith, will continue to be central to his campaign.

"He is who he is and that wouldn't be the right thing to do to change it," Biundo said. "We're going to continue going like we're going."

If Santorum starts raising more money, he may be able to rely more on TV ads than he did in Iowa. There, his limited finances forced him to stake his campaign on old-fashioned retail campaigning. He appeared in Pizza Ranches and diners, community centers and small businesses, to tout his conservative bona fides and make his case, county-by-county, voter-by-voter.

The payoff was late, but it came. Last Wednesday, about 50 voters and a handful of reporters gathered at a cafe in Dubuque to politely listen to Santorum make his case at his 358th town hall. Two days later in Ames, a throng of 70 reporters, photographers and cameraman mobbed Santorum as he made his way through Buffalo Wild Wing's Grill and Bar. Santorum seemed astonished, and apologized to patrons for interrupting game day.