Columbia, S.C. — Fighting to regain momentum in the South Carolina primary, Rick Santorum has shown little of the pizzazz that has characterized so many of the poll frontrunners this cycle.

“I may not be flashy and have a bunch of applause lines,” he admitted Tuesday, speaking at the Flight Deck restaurant in Lexington, S.C. “But what I’ve got is good, solid principles and I’m not changing my mind every ten minutes.”

In a navy sweater vest, his name embroidered on the upper right, Santorum earnestly and aggressively makes the case that he is the candidate around whom South Carolina conservatives should rally.

“South Carolina has a chance to nominate someone . . . who reflects their values,” Santorum says, speaking in a room papered with photographs of old military planes, to an audience clustered in booths and rows of chairs. “Don’t compromise.”

“The best chance to win this election is to not compromise,” he adds. “The country is looking for leadership. They’re not going to be looking for someone who can manage just a little better than the guy that’s in there now.”

Long before his Iowa surge, Santorum had shown at debates a willingness to go after his rivals. Now a top-tier candidate himself, he’s just as willing to throw punches. “Newt’s a friend of mine, but Newt is great in a think tank, coming up with a lot of different policy ideas, but as far as leadership, look at when the two of us were in leadership,” Santorum says, arguing that conservative organizations trusted him to fight for the issues they cared about from his perch in the Senate. In contrast, “three years into the speaker’s speakership, there was a conservative revolution against Newt trying to throw him out because he wasn’t advancing conservative [causes].”

As for Romney, Santorum argues that the former Massachusetts governor is “timid and, at best, inconsistent with respect to the issues we’re dealing with, and on the wrong side of many issues, like health care, the Wall Street bailouts, and global warming.”

Asked about Ron Paul, Santorum launches into an extended discussion of the differences between the conservative and libertarian outlooks on the Constitution. But at the end of his riff, he references Monday night’s debate, talking about Paul’s attempt to make a distinction between military spending and defense spending. “If someone can write me a memo on the difference, I’d appreciate that,” Santorum quips.

In Iowa, Santorum distinguished himself from the pack by pointing to his extensive retail politicking in the state, including visits to all 99 counties, a feat matched only by Michele Bachmann. In South Carolina, he has no such edge over his rivals.

And the chosen focus of his remarks, at least at this particular event, is perplexing. At the Lexington town hall, before opening up the floor to questions — usually a time when candidates deliver a brief sketch of their views on a wide range of issues — Santorum dives into a prolonged discussion of Social Security. He uses the topic as a way to distinguish himself from Romney and Gingrich, but he also delves deep into the details, rattling off factoids such as the percentage of seniors living below the poverty line, and musing on the fiscal benefits of pushing Social Security eligibility back just one or two months from age 62.

The questions after his remarks are wide-ranging, touching on topics from energy to immigration, and Santorum deftly handles them. Retiree Jane Flythe was struck by Santorum’s sincerity. “This man answers questions directly and right away,” she remarked. “You can’t always trust what everybody says. But I think he means it.” After commenting that she liked Gingrich, Flythe admitted she had lingering concerns about the former Speaker, saying she was “not comfortable with him because of his past and his changing his views.”

Is it enough? Santorum is currently lagging in the polls, just edging out Paul for third in the Real Clear Politics average. With Romney and Gingrich 17 points and 7 points ahead, respectively, Santorum needs to find a way to captivate the Palmetto State’s Republicans in the next few days. Further complicating his efforts, Gingrich seems to be gaining momentum, winning praise for his hard-hitting, crowd-pleasing debate performance Monday night. Tuesday night, when Santorum spoke after Gingrich and Perry at an event hosted by the South Carolina Chamber of Commerce, he failed to ignite the crowd the same way his rivals did.

“Newt stole the show today, definitely. He had that audience, and he was very convincing that he knew what he was talking about and would be very comfortable as president,” observed Shirley Hinson, director of government relations for the College of Charleston and former South Carolina House member. Hinson, who is leaning toward voting for Gingrich, commented that Santorum’s speech gave her the impression that he was “in over his head right now” and “lukewarm.” She also said the audience didn’t react as enthusiastically to Santorum, who spoke last: While Perry and Gingrich got multiple standing ovations from the audience, Santorum got only one, when he first came onstage.

Santorum did get a boost from endorsements this weekend, when he won the majority of votes cast at a meeting in Texas of top social-conservative and evangelical leaders. And as his attendees in Lexington showed, he has strong appeal for social conservatives, who make up a significant chunk of the South Carolina electorate.

Speaking about why he prefers Rick Santorum over Newt Gingrich or Rick Perry, the restaurant’s manager, Ted Stambolitis, cites “his stand on Christian values, that he doesn’t deviate from that.” The other candidates have good morals, Stambolitis adds, but it’s Santorum who seems to hold them “more firmly than anybody else.” Carrie Trent, a college student from Columbia, S.C., initially was leaning toward Perry, but is now volunteering for Santorum. “Number one, he’s pro-homeschooling,” Trent (who was homeschooled) says of Santorum. “Number two, I feel like he’s the most pro-life candidate. And number three, he’s pro-guns.”

With Michele Bachmann out and Rick Perry lagging in the polls, Santorum is already the natural choice for such voters. But he has to increase his support among other Republican voters, a tricky task without Gingrich’s rhetorical chops and Romney’s aura of inevitability. But he is expending all his effort, campaigning hard — he ruefully noted in Lexington that he was running on three hours of sleep — and maintaining a grueling event schedule.

In Lexington, Santorum was introduced by state senator Larry Grooms, a former Perry supporter. Grooms had a warning for those assembled, his sincerity strengthened by his own decision to switch his endorsement from Perry to Santorum. Noting the outcome of the 2008 cycle, when John McCain beat Mike Huckabee to win South Carolina, Grooms ruefully observed, “We probably made a mistake in South Carolina four years ago by splitting the conservative vote.”

But Grooms also saw a chance for the Palmetto State’s conservatives to redeem themselves.

“This race is not just about what happens in South Carolina,” he added. “Because if we can coalesce and make sure the votes are behind Rick Santorum, then, without a doubt, that would send a message very loudly going into Florida.”

— Katrina Trinko is an NRO reporter.