Slate editor Jacob Weisberg threw down the challenge after reviewing some of Joseph Smith's more extravagant assertions. "He was an obvious con man," Weisberg wrote. "Romney has every right to believe in con men, but I want to know if he does, and if so, I don't want him running the country." That argument, counters author and radio host Hugh Hewitt, amounts to unashamed bigotry and opens the door to any person of any faith who runs for office being called to account for the mysteries of personal belief. He has published A Mormon in the White House?, a chronicle of Romney's rise as business genius, Olympic savior, political star. But Hewitt has a religious mission as well when he cites a survey in which a majority of Evangelicals said voting for a Mormon was out of the question. If that general objection means they would not consider Romney in 2008, Hewitt warns, then prejudice is legitimized, and "it will prove a disastrous turning point for all people of faith in public life."

The Mormon question has settled in right next to the issue of whether a twice-divorced man has credibility discussing family values or whether changing one's mind on an issue like abortion is a sign of moral growth or cynical retreat. Unlike in 1960, today the argument is less about the role of religion in public life than in private. It is about what our faith says about our judgment and how our traditions shape our instincts--and about what we have the right to ask those who run for the highest office in the land.

Whenever the subject of Romney's "Mormon problem" arises, a whole host of commentators offer the same solution: all Romney has to do is "pull a J.F.K.," they say, meaning he needs to make a game-changing speech of the kind Kennedy delivered in September 1960 to the growling Protestant ministers of greater Houston. Kennedy declared that he viewed the separation of church and state as sacred; his religious beliefs, he said, were his private affair. "But if the time should ever come," he vowed, "... when my office would require me to either violate my conscience or violate the national interest, then I would resign the office." Romney has echoed Kennedy's sentiments, declaring that he would no more take orders from Salt Lake City than Kennedy would from Rome. But he can hardly suggest to the devout voters of the G.O.P. base that religious views don't matter, don't warrant discussion or don't affect one's conduct in office. These are voters inclined to think the wall of church-state separation is too high; it is certainly not one any candidate can hide behind. So his challenge is to draw the lines about what's relevant and what's not.

Compared with the Roman Catholic Church, which had 42 million U.S. members in 1960, the Church of Jesus Christ of Latter-day Saints (LDS) is newer and less familiar, its rituals more private. Romney supporters are offering Mormonism 101, emphasizing hard work, clean living and shared family values, to address the concerns of the 29% of Americans who say they would not vote for an LDS member for President. But when it comes to religiously conservative voters, the more people learn, the greater Romney's problem may become. And he will have to decide whether he's willing to provide the kind of public theology lesson that no other candidate has been asked to deliver.

Many Evangelicals have been taught that Mormonism is a cult with a heretical understanding of Scripture and doctrine. Mormons reject the unified Trinity and teach that God has a body of flesh and blood. Though Mormons revere Christ as Saviour and certainly call themselves Christians, the church is rooted in a rebuke to traditional Christianity. Joseph Smith presented himself as a prophet whom God had instructed to restore his true church, since "all their creeds were an abomination in his sight." He described how an angel named Moroni provided him with golden tablets that told the story (written in what Smith called "reformed Egyptian" hieroglyphics, never seen before) of an ancient civilization of Israelites sent by God to America. The tablets included lessons Jesus taught during a visit to America after his Resurrection. Smith was able to read and translate the tablets with the help of special transparent stones he used as spectacles. He published them as the Book of Mormon in 1830.

Twelve years later, Smith explained to a Chicago newspaper that "ignorant translators, careless transcribers or designing and corrupt priests have committed many errors" in the Bible, which he revised according to God's revelations. Mormons were subject to persecutions, and in 1844, as he was running for President, Smith was murdered by an angry mob. His successor, Brigham Young, led followers to Utah, the church proceeded to grow rapidly, and Mormon leaders were identified by the church as God's prophets on earth.

At all but the top level, the church is sustained by Mormon men volunteering as lay leaders. Romney was bishop of a ward, or congregation, and eventually president of a stake in Boston, meaning he was responsible for 14 wards with a total of some 3,000 members. Women cannot serve in priestly roles, nor could African Americans until a new revelation brought a change of policy in 1978. Should Romney have to account for such church practices? When he married Ann, a Mormon convert, in 1969 in the temple in Salt Lake City, her family could not attend the ceremony since only Mormons are allowed inside. A separate ceremony was held for "gentiles," as non- Mormons are called.

Conservative Christians don't much like the idea that the Bible is corrupted or that its truths could be updated. The conflicts run deep enough that in 2001 the Vatican ruled Mormon baptisms invalid, and even the more liberal Presbyterians and United Methodists require that Mormons looking to convert be rebaptized. Southern Baptists have called Utah "a stronghold of Satan," and there are many bookshelves' worth of anti-Mormon literature in circulation. The church's aggressive missionary work is a particular challenge to other professing churches, which believe that converts to Mormonism are not truly saved.

But old traditions of theological hostility conflict with constitutional traditions of religious tolerance and a modern trend toward political détente. When Jerry Falwell founded the Moral Majority in 1979, he was happy to welcome conservative Catholics and Mormons and Jews to increase his organization's throw weight on social issues. The fact that Romney personally emphasizes family, service and sobriety and opposes abortion and gay marriage has led some evangelical leaders to adopt a kind of "Don't ask, don't tell" policy when it comes to details of his faith. Romney has held quiet meetings around the country, and they have come away, by and large, impressed. "Southern Baptists understand they are voting for a Commander in Chief, not a Theologian in Chief," says Richard Land, president of the Southern Baptist Convention's public-policy arm. "But he's gotta close the deal. Only Romney can make voters comfortable with his Mormonism. Others cannot do it for him."

They're certainly willing to help, however. Pat Robertson invited Romney to give the commencement address at his Regent University, and the group Evangelicals for Mitt argues that religious conservatives are just as capable of separating faith and politics as liberal Democrats were when they elevated the highest-ranking Mormon in politics: Democratic Senate majority leader Harry Reid.

Romney's strategists are well aware that the deadliest campaigns in Republican primaries are often the ones waged below the radar. But in this age it is impossible to track every scurrilous e-mail or answer every blog assault. "There are caricatures that pick some obscure aspect of your faith that you never even think about and assume that it was the central element of the church," Romney says, noting that Mormon leaders past and present "said all sorts of things, but they're not church doctrine." Both Romney and wife Ann regularly make a punch line of the fact that he's the only leading Republican contender who is still on his first marriage. And for the record, Romney's great-grandfather, who had five wives, was the last polygamist in the family line.

That still leaves the concerns of more secular voters. Weisberg observes that modern political discourse seems to permit the exploration of candidates' every secret except their most basic philosophical beliefs: "The crucial distinction is between someone's background and heritage, which they don't choose, and their views, which they do choose and which are central to the question of whether someone has the capacity to serve in the highest office in the country." He would raise the same concerns, he notes, about a Jew or a Methodist who believed the earth is less than 6,000 years old. Weisberg's characterization of Mormonism as "Scientology plus 125 years" did not stop Romney from naming L. Ron Hubbard's Battlefield Earth a favorite novel. "Someone who believes, seriously believes, in a modern hoax is someone we should think hard about," Weisberg argues, "whether they have the skepticism and intellectual seriousness to take on this job."

Hewitt counters that Romney is facing a double standard, born of a barely hidden bias. "It is unreasonable to demand that a Mormon candidate expose and defend his deepest beliefs in rational terms in order to reassure voters that he is of sound mind," he says. He warns Evangelicals hostile to Romney's religion against colluding with those he sees as hostile to all religions. "The secular left that does not like people of faith in the public square is very happy to have a group of Fundamentalists raise this issue and be a battering ram," Hewitt argues. But if purely theological challenge becomes acceptable, he says, your own theology will be next: Which miracles do you believe in; what about this contradiction in Scripture?

Romney's inspiration going forward may come less from Kennedy than from Dwight Eisenhower, whom Romney reveres to such an extent, he told the Atlantic Monthly, that he asked his grandchildren to call him "Ike" and Ann "Mamie." It was Eisenhower who presided over the first National Prayer Breakfast, saw the addition of "under God" to the Pledge of Allegiance and IN GOD WE TRUST to dollar bills, and declared that "our form of government has no sense unless it is founded in a deeply felt religious faith, and I don't care what it is." There has always been a certain virtue in vagueness when it comes to presidential piety, and Eisenhower, a Presbyterian convert raised by Jehovah's Witnesses, benefited from discussing spirituality in the most general terms. Romney has repeatedly said that "I think the American people want a person of faith to lead the country. I don't think Americans care what brand of faith someone has."