TULSA, Okla. — Rick Santorum stirs his ever-growing crowds when he promises to right a country awash in “immoral debt” and to replace an administration he argues has “callousness toward life and family and faith.”

Of the GOP presidential hopefuls, Santorum is by far the most public and emphatic about his faith, drawing on his Catholicism and deeply held views on social issues as the foundation of his message. It serves to solidify his standing among religiously motivated voters — and subtly remind them of lingering reservations of opponent Mitt Romney’s spiritual background.

The former Pennsylvania senator is sure to find a receptive audience Friday in Washington, when he addresses the Conservative Political Action Committee’s annual gathering. But those remarks could sound a lot like Santorum’s speeches of late, particularly those delivered in a two-day visit to Bible Belt states of Texas and Oklahoma.

When the GOP field was at its fullest, several candidates were fighting to be the favorite of religious conservative voters. Now, Santorum is moving to consolidate that wing of the party, which could make him a force in places like Alabama, Kansas, Oklahoma and others on the upcoming primary calendar.

On Friday, he said he wanted to stick to substantive issues in the campaign and said he wasn’t inclined to resort to the kind of negative advertising that others have employed so far this year.

Santorum said in an interview on NBC’s “Today” show that he intended to stick to comparisons of his record with that of Romney, Newt Gingrich and Ron Paul, saying he wants to discuss things Americans care about, “not this back and forth that we’ve seen” so far.

Santorum said he doesn’t want to try to win the nomination “by personally attacking people.” His Southern swing, which ended Thursday with a stop at Oral Roberts University, followed a stunning three-state sweep Tuesday in Colorado, Minnesota and Missouri powered in part by his support among evangelical voters.