Editor's Note: CNN’s Joe Johns will explore the relationship between Newt Gingrich and social conservatives Thursday on The Situation Room at 5 p.m. ET.

By Dan Gilgoff, CNN.com Religion Editor

(CNN) - How big a stumbling block will Newt Gingrich’s three marriages and admission of an affair pose to his efforts to win so-called values voters?

“It’s a huge hurdle,” said Richard Land, the public policy chief for the Southern Baptist Convention, the county’s largest evangelical denomination.

“I must have asked 500 Southern Baptists about this in individual conversations,” Land said. “Evangelical men are likely to give him the benefit of the doubt. I find an implacable wall of resistance among evangelical women.”

As he announced Wednesday that he'll seek the 2012 Republican presidential nomination, it's clear that Gingrich is aware of the huge role religious conservatives play in the GOP primaries. But he also knows that his past presents challenges to winning them over.

“In meetings with pastors, the issue always comes up,” said Rick Tyler, Gingrich’s spokesman.

“And he answers it straightforwardly, courageously, without making excuses,” Tyler said. “Once they understand that he, like them, relies on his faith to get him through every day, they can get beyond it and hear his message. It turns out that pastors really are in the business of forgiveness.”

In recent years, Tyler has spearheaded Gingrich’s stepped-up campaign to organize evangelicals and Catholics at the grass roots - and to bring them closer to fiscal conservatives through efforts like the Tea Party movement. Tyler says that campaign will be especially important in early caucus and primary states like Iowa and South Carolina, where evangelicals represent huge voting blocs.

“I’ve been with Newt as he’s met with literally thousands of pastors; he’s made it an ongoing part of our travel agenda,” Tyler said.

On Wednesday morning, hours before he announced his campaign for the presidency via Twitter, Gingrich addressed the National Hispanic Prayer Breakfast on Capitol Hill.

In recent years, Gingrich has also made promoting religion in public life a central part of his message. He says a 2002 federal court ruling against reciting the Pledge of Allegiance in public schools because of its “under God” clause was a wake-up call.

At a speech to a Texas megachurch in March, Gingrich said that the United States will be a “secular atheist country, potentially one dominated by radical Islamists,” in a matter of generations unless Americans fight back against secularization.

Although religious conservatives are likely to respond to that message, the question for Gingrich is whether they’ll accept the messenger.

Gingrich's first marriage ended after he discussed the details of the divorce with his wife while she was recovering from cancer surgery. He married again in 1981 and was divorced in 2000, when he married the young congressional aide with whom he had had an affair.

Some accused Gingrich of hypocrisy for cheating on his wife around the time the House was impeaching President Bill Clinton for lying about his White House affair with Monica Lewinsky.

Many religious Americans may be apt to forgive him.

“Among evangelicals, the drama of sin and redemption is well understood,” said John Green, an expert on religion and politics at the University of Akron. “The question is how effectively he can explain that he’s not the same person he was back then.”

Gingrich would not be the first presidential candidate to overcome doubts among religious conservatives because of perceived personal transgressions.

In 1980, Ronald Reagan became the first divorced person to win the White House, with lots of help from evangelicals who’d supported Jimmy Carter, a Southern Baptist, four years earlier.

“Newt simply needs to address the past in an authentic way that makes it clear he is a changed man,” said Ralph Reed, chairman of the Faith and Freedom Coalition, “and I believe the overwhelming majority of social conservative voters will be fair-minded and forgiving.

“Most important, he needs to talk about how he has found peace and meaning through a personal relationship with Christ, that his marriage has never been stronger and that he has never been closer to his children and grandchildren,” said Reed, who once led the Christian Coalition.

Gingrich has apologized for his past behavior in interviews and usually appears in public with his wife, Callista. Gingrich has also spoken about how Callista helped lead him to convert from Protestantism to Catholicism in 2009.

“What evangelicals see in that (conversion) story is God at work,” Tyler said. “He went to Mass with Callista as a supportive spouse, and evangelicals have told me they think that’s right where God wanted him. Over time, it had a powerful effect.”

Still, some top religious conservatives say Gingrich still has a lot of work to do to win the votes of many conservative evangelicals and Catholics. The Southern Baptist Convention’s Land said he told Gingrich late last year that he needs to address his personal behavior in a major address.

“The only chance of clearing this hurdle is to give a major speech in some pro-family forum," Land said, "in which he imagines himself to be sitting directly across from an evangelical woman and convinces them that he deeply regrets his behaviors.

"That he understands how hurtful and destructive it was and that he has apologized to the people involved and is happily married and devoted to his wife," Land continued. "And that, whatever happens, there will be no sexual scandal in the Gingrich White House.”

Land says Gingrich told him he’d think about it.