The atmosphere was tense as the handsome presidential candidate from Massachusetts rose to address an audience packed with Protestant conservatives that he knew had serious doubts about the state of his soul.

We're not talking about Mitt Romney's recent trip to Virginia Beach to deliver the commencement address at Regent University. For political insiders, the only controversy in that speech was when he said, "I want to offer my sincere thanks to Dr. Pat Robertson for extending me the honor of addressing you today."

No, the daring campaign address that politicos are still discussing was the one John F. Kennedy delivered in 1960 to the Greater Houston Ministerial Association, the speech in which he erected a high wall of separation between his public political life and his private Catholic faith.

"I believe in an America," said Kennedy, "that is officially neither Catholic, Protestant nor Jewish - where no public official either requests or accepts instructions on public policy from the pope, the National Council of Churches or any other ecclesiastical source - where no religious body seeks to impose its will directly or indirectly upon the general populace or the public acts of its officials - and where religious liberty is so indivisible that an act against one church is treated as an act against all.

"For, while this year it may be a Catholic against whom the finger of suspicion is pointed, in other years it has been, and may someday be again, a Jew - or a Quaker - or a Unitarian - or a Baptist."

Or a Mormon? That's the question facing legions of evangelicals as they gird their loins for battle in the Bible Belt political primaries. They are waiting to see if Romney will publicly address their concerns about his deep Mormon faith.

That didn't happen at Regent, where the candidate stuck to marriage, parenting, public service and positive thinking. There was one clear religious reference, when he referred to the April 16 shootings at Virginia Tech.

"We're shocked by the evil of the Virginia Tech shooting," said Romney. "I opened my Bible shortly after I heard of the tragedy. Only a few verses, it seems, after the Fall, we read that Adam and Eve's oldest son killed his younger brother. From the beginning, there has been evil in the world."

Regent was a signpost in Romney's quest to calm evangelical fears, in part because the campus contains the headquarters of Robertson's Christian Broadcasting Network - which addresses Mormonism in its "How Do I Recognize a Cult?" Web-site page. It states, for example, that the Church of Jesus Christ of Latter-day Saints is a "prosperous, growing organization that has produced many people of exemplary character. But when it comes to spiritual matters, the Mormons are far from the truth."

That passage is mild compared to the incendiary language common among many Christian conservatives. Bill Keller of LivePrayer.com, for example, bluntly states that the teachings of the "Mormon cult are doctrinally and theologically in complete opposition to the Absolute Truth of God's Word. There is no common ground. If Mormonism is true, then the Christian faith is a complete lie."

Mormons do believe that the Old and New Testaments - as read by traditional Christians - are packed with errors and that Mormonism is the one true faith. Mormons believe that their president is a living prophet and that faithful mortals, in the next life, can achieve godhood. Thus, Mormons reject or redefine the Trinity, teaching that this world's Father God has both a literal body and a literal wife.

These are not the issues that obsess typical voters, but they are important to many Christian leaders who yield great influence in the public square. The Vatican, for example, refuses to recognize the validity of Mormon baptisms.

"There are valid questions that Romney will have to answer," said veteran religion writer Richard Ostling, co-author of "Mormon America: The Power and the Promise."

"People need to know, 'Is this man going to take orders from Salt Lake City? Are there elements of Mormon theology that will affect public policy?' ... But before he gets to those questions, Romney may have to say, 'We have different doctrines. We have different scriptures. ... We even have different concepts of God.' He has to know that he can't just say, 'We all have the same faith.' That is not going to work."

Terry Mattingly is director of the Washington Journalism Center at the Council for Christian Colleges and Universities and leads the GetReligion.org project to study religion and the news.