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The Iowa caucuses Tuesday elevated Rick Santorum, once a virtual unknown, into the national spotlight. But among the questions stemming from his newfound popularity is whether the truck-riding campaigner can sustain his momentum and weather the attacks to come.

Two of  Santorum's most obvious disadvantages moving forward are money and infrastructure, especially compared to front-runner and main rival Mitt Romney.

Santorum's super PAC - the Red, White and Blue Fund - spent a little more than $400,000 on two ads for him in Iowa, which pales in comparison to the $4.6 million outside groups spent on Romney. Even Rick Perry had a substantial money advantage, with his super PAC giving him $3.7 million worth of help in Iowa.

Santorum and Romney spent about an equal amount of their own money in Iowa. The former congressman spent a total of $1 million on his campaign in Iowa, compared with the $1.1 million Romney spent on ad buys. But unlike his opponent, Santorum lived in Iowa for months and visited all 99 counties, while Romney conducted a whirlwind, seven-day last-minute campaign leading up to the caucuses.

The former senator from Pennsylvania doesn't even have a bus. He trekked across Iowa a la Scott Brown in a truck driven by one of his supporters. Reality-television stars, the Duggars, wrapped their family bus in a "Santorum for President" sign. Upon seeing it, Santorum even said, "We can't afford this," according to an Iowa Republican activist, until he was told it belonged to the stars of "19 Kids and Counting."

The money factor obviously did not affect Santorum in Iowa, where he was narrowly defeated by Romney. But it could be a game-changer in the primary states of New Hampshire and South Carolina, where Santorum has less of a presence than in Iowa. That was evident in a fundraising appeal by Santorum sent to his supporters this morning,

"The next test is New Hampshire … a state Mitt Romney has campaigned in for over four years. This is why I need your immediate support," Santorum wrote.

Republican analysts in South Carolina say Santorum has been successful in appealing to undecided conservative voters who are not necessarily activists, but he has a long way to go in proving that he's the right candidate to beat President Obama.

"He has certainly spent a lot of time here and I think he has a great deal of support with those in the social conservative community, which makes up a decent amount of the Republican primary," said Republican consultant Hollis "Chip" Felkel, who last worked in the Bush-Cheney campaigns in 2000 and 2004.

"His struggle will be whether or not he can do well enough in New Hampshire to show some increased viability," Felkel added. "I think he's got to continue to show strength in New Hampshire. I don't think he has to necessarily win New Hampshire - he's not expected to - but he's got to finish strong."

Santorum lacks the kind of sophisticated infrastructure and resources his rivals enjoy in New Hampshire and South Carolina.

And then he has to worry about how to confront new lines of attacks that are likely to emerge. Santorum has thus far stayed mostly under the radar, but the strong show of support in Iowa could change that rapidly. He will face tough questions as one of the new front-runners when he takes to the stage in ABC's debate Saturday and a CNN debate Sunday.

"I think a lot will depend on how Santorum will handle the pressure of being in this [top] position," Felkel said.

Santorum is also finding himself on the defensive when it comes to his stance on many conservative issues. His often-hawkish stance on abortion and gay marriage has been met with disapproval even by some in his own party. Santorum supports a blanket ban on abortion, even in cases of rape or incest, as well as criminal prosecution of doctors who perform abortions.

The former senator also advocates a constitutional amendment to ban gay marriages, even though he has spoken in favor of personal freedoms. Santorum has also said that, as president, he would bomb Iran's nuclear facilities if the country's leaders do not allow international inspections, a stark departure from non-interventionists such as Ron Paul.

Santorum is likely to take as much heat from the right as the left. Rick Perry already pounced on Santorum for voting to raise the debt ceiling and losing his congressional seat in 2006 to Bob Casey. He also pointed to Santorum's support of Democrat Arlen Specter in 2004 as a trouble spot for conservatives, and his work as a consultant for a lobbying firm that represents the Human Rights Campaign and Reform Immigration for America.

His opponents have also derided Santorum for an ad he made in 2006 touting his bipartisan work with liberal Democrats such as Sens. Barbara Boxer of California and Hillary Clinton of New York. He also will have to answer ethics questions about whether he received a preferred mortgage by a bank run by his campaign donors, and helped give federal funds to a real estate developer who backed his charity.

But Santorum is not letting such factors deter his campaign. His fundraising has more than tripled in the past week. He raised $1 million in the last 24 hours alone, almost exclusively from small dollar contributions, and the campaign is now running ads in New Hampshire and South Carolina.

The campaign will be hiring additional staff members focused on grassroots efforts, as well as volunteers in both states. His campaign manager, Mike Biundo, is from New Hampshire and, in South Carolina, Santorum is represented in 42 of 46 counties and has three offices there.

He also boasts a strong backing by Tea Partiers and evangelical Christians, both of which groups voted overwhelmingly for him in the Iowa caucuses. Continued Tea Party support could help boost his chances in the next primary states.

Santorum will also be helped by his blue-collar roots, which he continues to stress in his campaign, and his connection to Rust Belt priorities compared to Romney, who is touting his business acumen. In his speech Tuesday night, Santorum clearly distinguished himself from Romney, talking up his grandfather's work in the coal mines of Pennsylvania and "a great and just society," built from the bottom up.

With Rep. Michele Bachmann suspending her campaign and Perry hanging on by a thread, Santorum is presented with a new opportunity to prove that he can continue his success outside of Iowa and in the national sphere as the anti-Romney candidate.