There’s only one problem. Romney is a Mormon, a member of the Church of Jesus Christ of Latter-Day Saints (LDS). Mormonism was never an issue when Orrin Hatch ran for president, but Hatch was never talked up with even a smidgen of the seriousness that accompanies the Massachusetts governor. Yet each Romney profile plays down the Mormon issue. In a typical treatment, under the headline “Matinee Mitt,” John Miller admits in the National Review that some of Romney’s Republican opponents might highlight a few of “Mormonism’s doctrinal oddities,” but concludes that “there is no telling how this will play out,” and “it’s even possible to think that Romney’s Mormonism could become a hidden asset.”

It’s understandable that political observers want to think Romney’s religion wouldn’t be a problem. He’s an appealing candidate with compassionate conservative allure. Moreover, we would all like to believe that a politician’s religious affiliation isn’t an obstacle to higher office. There’s a general sense, particularly among the chattering class, that we’ve gotten past that. Didn’t Sen. Joseph Lieberman (D-Conn.) run on the Democratic ticket in 2000 with no problem? Aren’t there a handful of Catholic candidates among the field of potential Republican nominees for 2008?

Americans have indeed become more religiously tolerant, but the first Mormon to run for president will clearly have to change some minds. In the late 1960s, the percentage of Americans who said they would not vote for a Jewish or Catholic presidential candidate was in the double digits; by 1999, those numbers had fallen to 6 and 4 percent, respectively (roughly the same as the percentage of voters who say they wouldn’t vote for a Baptist). Compare that to the 17 percent of Americans who currently say they would have qualms electing a Mormon to the White House. That number hasn’t changed one whit since 1967, the year that Romney’s father considered a presidential run (he abandoned the effort after making a gaffe about how the military “brainwashed” him into supporting the Vietnam War).

Some of this anti-Mormonism is a fairly fuzzy sort of bias, based mostly on rumors and unfamiliarity and the vague feeling that Mormons are kind of weird. It’s a wobbly opposition that can be overcome by good public relations that defuses concerns about the religion and shifts focus to the personality of the candidate. This is how someone like Romney gets elected in a blue state like Massachusetts, where even Republicans are generally tolerant.

But moderate Republicans aren’t the ones who could derail a Romney candidacy. His obstacle is the evangelical base–a voting bloc that now makes up 30 percent of the Republican electorate and that wields particular influence in primary states like South Carolina and Virginia. Just as it is hard to overestimate the importance of evangelicalism in the modern Republican Party, it is nearly impossible to overemphasize the problem evangelicals have with Mormonism. Evangelicals don’t have the same vague anti-LDS prejudice that some Americans do. For them it’s a doctrinal thing, based on very specific theological disputes that can’t be overcome by personality or charm or even shared positions on social issues. Romney’s journalistic boosters either don’t understand these doctrinal issues or try to sidestep them. But ignoring them won’t make them go away. To evangelicals, Mormonism isn’t just another religion. It’s a cult.

The first time I ever heard about Mormons was in fifth grade, sitting in a basement classroom of my Baptist church, watching a filmstrip about cults. Our Sunday school class was covering a special month-long unit on false religions; in the mail-order curriculum, Mormonism came somewhere between devil worshippers and Jim Jones. Although most of the particulars are lost to me now, one of the images remains in my mind: a cartoon of human figures floating in outer space (an apparent reference to the Mormon doctrine of “eternal progression”) that appeared on the screen next to our pull-down map of Israel. Even at age 10, the take-away message was clear. Mormons were not like us, they were not Christian.

Evangelical opinions about the LDS Church haven’t changed so much since I watched that filmstrip more than 20 years ago. In 2004, Mormons were specifically excluded from participation in the National Day of Prayer organized by Shirley Dobson (wife of James Dobson, leader of the conservative Christian organization Focus on the Family) because their theology was found to be incompatible with Christian beliefs.

Mormons believe that they are the fully realized strain of Christianity–hence the “latter-day saints.” They acknowledge extra-biblical works of scripture (such as the Book of Mormon and the Doctrine and Covenants), follow a series of prophets who claim to have received divine revelations, and teach that God inhabits an actual physical body. This is all blasphemy to evangelicals; they argue that “the Bible explicitly warns against adding to or detracting from its teaching” and refer to the revelations as “realistic deception[s] by the Devil himself.”

Evangelical Christians consider Mormonism a threat in a way that Catholicism and even Judaism are not. The LDS Church, they charge, has perverted Christian teachings to create a false religion. As John L. Smith, a Southern Baptist who runs Utah Mission–an organization that tries to convert Mormons–told Christianity Today: “Mormonism is either totally true or totally false. If it’s true, every other religion in America is false.” To be tolerant of Mormonism is to put evangelical Christianity at risk. And to put a Mormon in the White House would be to place a stamp of approval on that faith.

Southern Baptists have been particularly vocal about labeling the LDS Church a “cult.” In 1997, the denomination published a handbook and video, both with the title The Mormon Puzzle: Understanding and Witnessing to Latter-day Saints. More than 45,000 of these kits were distributed in the first year; the following year–in a throwing down of the proselytizing gauntlet–the Southern Baptist Convention held its annual meeting in Salt Lake City. Around the same time, a speaker at the denomination’s summit on Mormonism declared that Utah was “a stronghold of Satan.” When Richard Mouw, president of the evangelical Fuller Theological Seminary, tried to repair relations with the LDS community by apologizing on behalf of evangelicals during a speech in the Mormon Tabernacle last year, his conservative brethren lashed out. Mouw had no right, they declared in an open letter, to speak for them or apologize for denouncing Mormon “false prophecies and false teachings.”

In the wake of Romney-mania, one prominent evangelical has sung a slightly different public tune. Charles Colson told the Weekly Standard in June that he “could in very good conscience support Romney” as a fellow “social conservative on most of the issues we care about.” As recently as late February, however, Colson reminded his radio listeners that “while Mormons share some beliefs with Christians, they are not Christians.” “I respect Mormons and work with them,” he said, “but we can’t gloss over our fundamental differences.” Asked about Colson’s apparent change of heart, Richard Cizik of the National Association of Evangelicals (NAE) told me, “I think Chuck was probably saying the politically correct thing.”

“Most evangelicals still regard Mormonism as a cult,” Cizik explained. “That will shape, I’d imagine, their reactions to Romney as a candidate for the White House.” Cizik, who serves as the NAE’s Vice President for Governmental Affairs, is the only evangelical leader who was brave enough to break from the script and talk to me on the record about what his members really believe. But many others I spoke with shared his views. One longtime political observer put it this way: “Publicly, it’s not an issue. Privately, it’s a big damn issue.”

These latent evangelical concerns about Mormonism don’t pose much of a problem in the general course of political and social life. In the real dynamics of a campaign, though, they are huge vulnerabilities, waiting to be exploited. To see how this might happen, take a look at the 2002 gubernatorial race in Arizona. In that campaign, Democratic state attorney general Janet Napolitano faced popular Republican congressman Matt Salmon for the open governor’s seat. A month before election day, the race was neck-and-neck, when a third-party candidate named Dick Mahoney began running a television commercial that raised Salmon’s Mormonism in the context of a Mormon fundamentalist sect that openly practices polygamy on the Arizona/Utah border. The ad was offensive and was immediately denounced by religious and political leaders. It was also effective.

On election day, Salmon lost to Napolitano by a razor-thin margin. Napolitano won in part by picking up votes among moderate female voters, but also because Salmon ran far behind congressional candidates in the most conservative and heavily evangelical districts. In each of these precincts, his support was between 10 and 20 points lower than right-wing congressmen Trent Franks and Jeff Flake. Exit polls aren’t available for 2002, but a look at the precinct results makes it clear that some of these conservative voters must have even split their tickets, casting a vote for Napolitano while also backing the extremely conservative congressional candidate.

Salmon lost evangelical votes at the polls even though he enjoyed the backing of evangelical leaders, some of whom denounced the anti-Mormon ads. Arizona Republic political columnist Rob Robb told me that Salmon’s support from evangelical leaders “did not translate into support among evangelicals at the grassroots.” “Around here,” he said, echoing my childhood experience, “evangelicals are regularly instructed that Mormonism is a cult.”

Absent a third-party challenger, it’s hard to imagine this kind of defection happening to Romney in a general election for president. Mormons may be considered cult members, but Hillary Clinton is still the bride of the devil, after all. But the general election isn’t where Romney would be most vulnerable. Long before he reaches that point, he will have to prevail in the GOP primaries. Nearly everyone I spoke to brought up the example of the 2000 primaries, in which Bush surrogates went after Sen. John McCain’s (R-Ariz.) candidacy by placing calls to voters in South Carolina that claimed he had fathered an illegitimate black child and implied that his wife was addicted to drugs.

It’s likely that Romney’s primary opponents and prominent religious leaders will publicly take the high road, remaining mum on the issue of his Mormonism. But, says Marshall Wittman, former political director of the Christian Coalition and later an aide to McCain, “so much in the primaries takes place under the radar. It’s never publicly said, but it takes place in emails and word of mouth.” The push-poll script writes itself: “Would you be more or less likely to vote for Mitt Romney if you knew he was a Mormon, and that Mormons believe in polygamy?”

The worst may come not from the push polls but from the preachers. Churches that show movies portraying Mormonism as a cult or that sponsor crusades to convert Mormons aren’t likely to turn around during the campaign and say, “Oh, never mind.” Especially not when there are other candidates to choose from. “That’s the critical factor here,” Cizik told me. “There are so many options. It’s not as if there aren’t other candidates running who share nearly identical credentials. Is he such a compelling candidate that people are willing to overlook his religious beliefs? That’s a pretty high bar.” The question isn’t whether evangelical leaders could support a Mormon, but whether they would back a Mormon over an equally appealing Protestant or Catholic Republican. It’s hard to see evangelicals lining up behind Romney instead of, say, Virginia Sen. George Allen.

All of this leaves Romney in a real pickle. Thus far, he’s tried to follow in the tradition of other Massachusetts politicians and “pull a John Kennedy,” declaring personal faith irrelevant to his qualifications for office. This is a nonstarter. We live in a political era in which, thanks largely to Republicans, candidates are virtually required to talk openly about their religious views. There is no way a Republican, especially in a GOP primary, can avoid the issue–if for no other reason than the press won’t let them.

Indeed, it’s already begun. “How Mormon are you?” Sridhar Pappu asked Romney for his Atlantic Monthly profile. Romney’s answer sounded like it could have come from George W. Bush: “You know, the principles and values taught to me by faith are values I aspire to live by. [They] are as American as motherhood and apple pie. My faith believes in family, believes in Jesus Christ. It believes in serving one’s neighbor and one’s community.” That kind of vague answer works for Bush, but Bush is a Methodist. In his interview, Pappu continued to press Romney about the particulars of Mormon practice. Cornered, the governor replied tersely. I’ll just say those sorts of things I keep private.” At that point, Pappu dropped the issue. But the next reporter won’t, nor the next, nor the next.

By now, reporters are used to Protestant candidates, but they eat up any chance to explore a new religious angle. They peppered Lieberman with questions in 2000 about whether he could campaign on the Sabbath and followed John Kerry to mass every week during the 2004 campaign to probe his views on the Eucharist.

As the first serious LDS presidential candidate, Romney is an oddity. News outlets will feature charts comparing Mormon theology to Christian doctrine, and stories detailing various dietary and clothing restrictions. Again, this may help demystify Mormonism for average voters who may be generally uneasy about the faith, but it will only serve to remind evangelicals of the differences between the two religions. Indeed, Romney faces an unwinnable dilemma: The more information that circulates about the specifics of his faith, the more hesitant evangelical voters will be to support him.

Conservatives are beginning to worry about Romney’s viability with evangelicals, even if they’re not saying so publicly just yet. One LDS politician has been quietly making the rounds to Washington wise men to get their sense of what evangelical opposition would mean for Romney in the primaries. Meanwhile, Robert Novak, who is as closely connected to conservative sources as anyone in the nation’s capitol, wrote in June that Romney’s Mormonism is “his one great liability as a presidential candidate.”

The tragedy–or, depending on your point of view, the irony–is that Mitt Romney may just be the most appealing candidate Republicans can field in 2008, the one most likely to win the White House by shoring up social conservatives and rallying business interests without frightening swing voters. Yet the modern GOP’s reliance on evangelical voters and its elevation of personal religiosity–strategies which have served the party so well in recent years–may doom the chances of this most promising candidate. Or, to put it in evangelical terms, it might be easier for a camel to pass through the eye of a needle than for Mitt Romney to win the Republican nomination.

Amy Sullivan

Amy Sullivan is a Chicago-based journalist who has written about religion, politics, and culture as a senior editor for Time, National Journal, and Yahoo. She was an editor at the Washington Monthly from 2004 to 2006.