(RNS) On a recent Sunday, Rep. Michele Bachmann offered a Pentecostal church in Iowa an intimate account of her pilgrimage from apathetic teenager to devout Christian whose faith has persevered through hardship, including a miscarriage.

But when a reporter asked about the churches her family has attended, the Republican presidential candidate went mum.

"We're not here to talk about anything other than just the church. Thank you," Bachmann, told IowaPolitics.com, referring to Des Moines First Assembly of God, where she recited her spiritual testimony before 500 fellow Christians -- and potential caucus voters -- on July 17.

The Minnesota congresswoman's eagerness to bare her soul but not the site of her Sunday worship seems to reflects a convergence of wider concerns: evangelicals' increasing aversion to religious labels, a dread of being caught with "pastor problems," and the cold political calculus of reaching the largest possible constituency.

"Today more evangelicals prefer a broader religious identity," said D. Michael Lindsay, president of Gordon College in Wenham, Mass. "Not one that is tethered to a particular denominational hierarchy, but rather one that stresses a personal relationship with Jesus and an active, vibrant faith."

Carrying the baggage of a Christian denomination -- and more than a few have ecclesiastical skeletons in their closet -- could also make it difficult to build political alliances across religious lines, added Lindsay, author of "Faith in the Halls of Power: How Evangelicals Joined the American Elite."

But it is crucial that candidates like Bachmann, who has placed her faith at the center of her campaign, are questioned about how and where that faith was formed, said Diane Winston, an expert on religion and the media at the University of Southern California.

"Since Michele Bachmann presents her religious beliefs as fundamental to her campaign, she opens them for public scrutiny," Winston said. "What she believes, where she goes to church and how she expresses her faith are all part of the public's right to know."

Bachmann caught a glimpse of the political difficulties denominations can present in 2006, when she was questioned about the Wisconsin Evangelical Lutheran Synod and its centuries-old belief that the papacy is the Antichrist.

Later, as her political profile increased, Bachmann and her family left WELS for Eagle Brook, a more mainstream evangelical church with four campuses in Minnesota. Bachmann officially left her Lutheran congregation on June 21, six days before she launched her presidential campaign.

An aide told the Christian Broadcasting Network that the Bachmanns' decision to leave WELS "came down to preference issues, as it does for so many evangelical families who occasionally change churches." Her campaign has not responded to repeated requests for comment.

Of course, Bachmann is not the first politician to change churches as her political star began to rise.

Dwight D. Eisenhower buried his family's roots as Jehovah's Witnesses and presented himself as a Presbyterian when he ran for president in the 1950s, according to Mark Silk, an expert on religion and politics at Trinity College in Hartford, Conn.

Eisenhower was concerned that Jehovah's Witness injunctions against saluting the flag and armed military service would brand the candidate as anti-American, scholars say, even though Eisenhower himself was a five-star general.

More recently, Barack Obama quit Chicago's Trinity United Church of Christ just before clinching the Democratic nomination in 2008, following months of controversy over the inflammatory rhetoric of his former pastor, the Rev. Jeremiah Wright Jr.

That same year, former Republican vice-presidential nominee Sarah Palin refused the label of "Pentecostal," even though she was baptized in an Assembly of God church and worshipped there for decades. Instead, Palin defined herself broadly as a "Bible-believing Christian" who now attends a "nondenominational Bible church."

Lindsay said Palin's move is mirrored by many successful evangelicals, who migrate from "spicy" religious traditions like Pentecostalism, where speaking in tongues and prayer healings are common, to more "vanilla" expressions of faith.

"Perhaps that's even more so the case with politicians," Lindsay said. "They want to cultivate that cosmopolitan sensibility, so they are very careful about the churches they are associated with."

Scholars like Silk hear echoes of Palin in Bachmann's reluctance to divulge specifics about her church background.

"I've got an idea that there's a memo out there to GOP candidates that they should just present themselves as `Christians,"' he wrote on his blog, Spiritual Politics.

"That's what white evangelicals increasingly prefer to call themselves, and it lets you evade all invidious denominational -- and doctrinal -- distinctions. Or even better, just talk about your recent prayer life."

Shaun Casey, an ethicist at Wesley Seminary in Washington, D.C., who advised Obama's 2008 campaign, calls the "evangelical" label a "flight from particularity."

"The devil is not in the `evangelical' title," Casey said. "It's in the details of your particular church history. But they can use that title to buffer against scrutiny."

But that scrutiny is an important element of assessing candidates for high office, argues Damon Linker, author of "The Religious Test: Why We Must Question the Beliefs of our Leaders."

"If you claim to be religious then you have a public duty to explain yourself," said Linker, the commentary editor at Newsweek/The Daily Beast. "There is nothing shameful about it. It should be on the table to talk about: What does your church teach? And do you agree with your church?"

Phil Dacosta, who is organizing for Bachmann in Georgia, said the congresswoman "did the right thing" in leaving her Lutheran church, but also doubted that it would matter much to voters.

The 42-year-old Southern Baptist from Atlanta said he cares more about how Bachmann has lived her life -- caring for foster children, fighting gay marriage and abortion, pushing schools to teach creationism -- than the church she attends.

"At the end of the day we know what she believes," Dacosta said.

"She believes the Bible is 100 percent true. There are always little things to disagree on, but the fundamentals are pretty much the same, and this is no time to quibble."