FLORENCE, S.C. - It was a day for the sacred and the secular on the Republican presidential campaign trail Sunday as candidates courted evangelical voters in churches and pressed their claims as the truest conservative on the weekly network political shows and during restaurant stops.

Former Pennsylvania Sen. Rick Santorum was hoping to capitalize on his weekend endorsement from a group of national religious conservative leaders, who called him the best candidate to unite the movement and stop front-runner Mitt Romney in Saturday's South Carolina primary.

"So South Carolina, vote your conscience. Vote your values," Santorum implored about 125 people in Percy & Willie's restaurant late Sunday afternoon. "Don't compromise . . . stand up and fight for what you know is right for this country."

In 2008, 60 percent of voters in the state's GOP primary described themselves as evangelical or born-again Christians in exit polls. With Santorum, former House Speaker Newt Gingrich, and Texas Gov. Rick Perry carving up the social-conservative vote, Romney is poised to win with establishment-oriented conservatives and moderate Republicans convinced he is the most electable against President Obama.

If he were to win here, it would be Romney's third victory in a row, after he edged Santorum by eight votes in Iowa on Jan. 3 and decisively won the New Hampshire primary last week, and conservatives fear he would become unstoppable.

"I think the only way that a Massachusetts moderate can get through South Carolina is if the vote is split," Gingrich said on NBC's Meet the Press. He added that his experience and debating skill make him the "strongest rival" to Romney, and he called for the former Massachusetts governor to release his tax returns.

The candidates, including libertarian Rep. Ron Paul, are scheduled to debate Monday in Myrtle Beach, broadcast on Fox News at 9 p.m., and to clash again Thursday in a CNN debate from Charleston. Former Utah Gov. Jon Huntsman reportedly will end his campaign Monday.

At a prayer breakfast in Myrtle Beach on Sunday, Perry talked of accepting Christ as his savior when he was 14 and asked religious conservatives for their backing. "Who will see the job of president as that of faithful servant to the American people, and the God who created us?" Perry asked. "I hope each of you will peer into your heart and look for that individual with the record and the values that represent your heart."

Perry and Gingrich used TV appearances to raise questions about Romney's former tenure as head of the investment firm Bain Capital. Romney has used the experience to say he is the candidate with the best understanding of the economy, claiming to have created 100,000 jobs.

Critics say that his accounting does not include jobs lost to layoffs and company closings.

"It's fair to raise the questions now, get them out of the way now to make sure that whoever we nominate is clear enough, public enough, accountable enough that they can withstand the Obama onslaught," Gingrich said on NBC.

Santorum, on CBS's Face the Nation and in campaign appearances, said that Romney does not provide a clear enough contrast because he implemented a health-care law in Massachusetts requiring that individuals buy health insurance, as Obama's national program does. "Romney's plan, as much as he'd like to say it's not, was the basis of Obamacare," Santorum said. "For us to give away that issue with Gov. Romney would be a case, in my opinion, of malpractice on the part of the primary voters."

Many social and religious conservatives distrust Romney because he had supported abortion rights and gay rights before seeking the presidency in 2008.

Romney took a rare day off the trail Sunday, and Paul was en route from his home in Texas for his first campaign event in South Carolina on Sunday evening.

At First Baptist Church in Columbia, Gingrich's two sisters attended Sunday school and the morning worship service on "Sanctity of Life Sunday," observed in Southern Baptist congregations nationwide to mark the 29th anniversary of the Roe v. Wade Supreme Court decision that legalized abortion.

The Rev. Wendell Estep urged worshipers to pray over their choice in the primary and to pick the candidate who would be best for the country and reflect their values. "We're losing our country as I knew it and many of you knew it . . . if we don't have a revival."

At Santorum's event in Florence later, Rick Bonnoitt said that Santorum did a "good job of swaying me" his way. "He put it pretty basic: how this country was founded on faith, and if we're going to move forward, we have to get back to that," said Bonnoitt, 55, of Darlington.

He had been backing Perry because of the job-creation rate under his administration in Texas, but said that Perry was slipping too far in the polls to be viable. He said he could still change his mind, but one potential choice was off the table: Romney.

"I just can't get a grasp on him, and it was the same way in '08," Bonnoitt said. "I just can't pinpoint it. He's a very accomplished person, but he's too slick, too. . . . He just doesn't do it for me."

Contact politics writer Thomas Fitzgerald at 215-854-2718, tfitzgerald@phillynews.com, or @tomfitzgerald on Twitter.