“Surely, secularists are wrong when they ask believers to leave their religion at the door before entering the public square.”

That 2006 quote comes from Barack Obama’s politically self-conscious second book, The Audacity of Hope, whose title was taken from a sermon by Rev. Jeremiah Wright. Of course, in this political era of cross-on-your-sleeve public religiosity, secularists have been in retreat since John Kennedy affirmed the wall of separation between church and state in his 1960 speech to the Houston ministers.

It is a near certainty that religion will show up in a prominent place in the public square of the 2012 presidential campaign. The relevant question is not whether it will appear, but when—and how campaign reporters should cover it.

The New York Times revealed last month in a story by Jeff Zeleny and Jim Rutenberg that a leading Republican admaker tried to sell a Super PAC donor on a $10 million ad campaign to highlight Obama’s past relationship with the sometimes incendiary Wright. The vitriolic (and untrue) birther attacks on Obama, which I wrote about last week, are linked to equally fabricated claims that the president is a closet Muslim.

This time around, though, the flashpoint is likely to be Mitt Romney’s religion. Romney’s Mormonism is entwined with his biography: Not only was he a missionary in France, but he also served as a bishop and stake president, overseeing a dozen congregations in the Boston area. As Boston Globe reporters Michael Kranish and Scott Helman conclude in their biography, The Real Romney, “The portrait of Romney that emerges from those he led and served with in the church is of a leader who was pulled between Mormonism’s conservative core views…and the demands…for a more elastic, more open-minded application of church doctrine.”

All this would be ho-hum material if Romney were a Methodist or an Episcopalian. But Romney’s church, with its polygamous past and its easily mocked missionary zeal (The Book of Mormon), is outside the American religious mainstream. And that means that we are just one incendiary Super PAC donor or one intemperate cable TV comment by a Democrat away from a major campaign flap over Mitt’s Mormonism. So with that in mind, what should the journalistic rules be regarding Romney’s religion?

As recounted by both Jodi Kantor in the Times and Jason Horowitz in The Washington Post, the Romney campaign suggests that when reporters write about the Republican’s Mormonism, they should think about how the passage sound if they substituted the term “Jewish.” Needless to say, the Romney campaign is not an impartial arbiter of journalistic coverage. In any case, this WWJLD (“What Would Joe Lieberman Do?”) standard has its limits. Yes, it would eliminate snide references to Joseph Smith’s religious revelation and constrain anyone sneeringly referring to Mormonism as a “cult” (Bill Maher, please pick up the white courtesy phone). But left unanswered is the deeper question of the role of Romney’s religious faith in understanding his political persona.

Recalling the 2008 furor over Jeremiah Wright and his pulpit cry of “God damn America,” it may be tempting to expansively claim that everything about a candidate’s religion is fair game in the heat of a presidential campaign. But that is, I believe, a misreading of the Wright stuff. Wright’s rhetorical excess mattered because he was more than just a minister to a presidential candidate; he was the pastor who, in Obama’s words, “helped introduce me to my Christian faith.” What mattered journalisticaly was Wright’s longstanding closeness to Obama, rather than his pastoral role. Obama in his autobiography, Dreams from My Father, put Wright on a pedestal, which made the minister’s subsequent comments politically relevant. The same principle would hold if Obama had gushed in print about a lawyer friend, who was an atheist with outré views.

Walter Shapiro just chronicled his ninth presidential campaign. He writes the “Character Sketch” political column for Yahoo News. Follow him on Twitter @WalterShapiroPD.