SALT LAKE CITY » As 20,000 Mormons streamed from the church conference center, a ragtag group of protesters stood across the street shouting that the Latter-day Saints were going to hell. Mormon families, who had gathered here for two days of speeches and spiritual guidance called General Conference, ignored the hecklers or laughed and kept walking.

This, after all, is a church accustomed to worse.

Yet, even with a resilience built over nearly two centuries as outsiders, church members are anxious about what’s ahead. Republican Mitt Romney is about to become the first Mormon nominee for U.S. president on a major party ticket. That will give them a chance like no other to explain their tradition to the public, but the church’s many critics will have a bigger platform, too. And the vetting will take place amid the emotion of what may well be a nasty general election.

"People who have opposed Mormonism forever will use this as an opportunity," said Robert Millet, a religion scholar at Brigham Young University who co-founded a pioneering evangelical-Mormon dialogue. "I don’t know if we’re ready for this kind of deluge."

At the Salt Lake City headquarters of the Church of Jesus Christ of Latter-day Saints, officials are preparing to defend the church.

It’s an effort that began before Romney officially announced his first, ultimately unsuccessful 2008 bid for the GOP nomination. Mormon officials met with journalists around the country about the church’s nonpartisanship. Leaders were worried that any statements they made to clarify doctrine would give the impression of aiding Romney.

That concern continues this election season. LDS officials have emphasized that the church doesn’t communicate with the Romney campaign. In a lengthy statement on their main website, Mormon leaders say the church does not "endorse, promote or oppose political parties, candidates or platforms."

The Latter-day Saints have been running a multimillion-dollar series of ads, called "I’m a Mormon," since 2010, to dispel stereotypes by telling the stories of individual Mormons. To avoid any appearance that the ads were meant to help Romney, the church didn’t buy ad time in Iowa and some other markets with early primaries, said Michael Purdy, an LDS national spokes­man. At the General Conference last month, led by the highest authorities of the church, there was no mention of the election across the pulpit.

"We’re just going to do what the church does, regardless of the election," Purdy said.

The neutrality message can be a hard sell since Mormons are known to be overwhelmingly Republican and more socially conservative than many other Americans. The impression was reinforced by Mormon contributions of money and volunteers for Proposition 8, the 2008 California measure to bar same-sex marriage. (LDS officials say they were advocating for a moral, not a partisan, issue.)

The church has long contended with conspiracy theories of Mormon plots to take over America, claims that have increased with Romney’s prominence. If the former governor wins the White House, however, several political scientists predict LDS officials would be more likely to pull back from any policy debates to avoid an appearance of undue influence, even when Mormons have a clear interest.

"There is a good chance that the main way a lot of leaders of the church will respond to the election of a Mormon to the presidency will be to stay as quiet and uninvolved in politics as possible and put as much daylight as possible between that president and the institutional church," said Russell Arben Fox, a political scientist at Friends University in Wichita, Kan., and a Mormon writer. "They’re a global church and have responsibilities all around the world. For them to appear to be lining up behind a Mormon president and endorsing his policies would just be bad for the church."

Despite their fears, Mormons acknowledge that Romney’s nomination will be a milestone like none before for the church.

Organized in 1830, Latter-day Saints were persecuted from their earliest days for their doctrine and support for polygamy, which Mormons renounced in 1890. A mob assassinated founder Joseph Smith in 1844, sending Mormons fleeing into the unsettled Mountain West. Theological differences with other faith groups — about scriptures, the nature of God and heaven — provided fodder for anti-Mormon bias over the years. Christian groups challenged the Mormon assertion that the church is part of traditional Christianity. One such group, the Utah Lighthouse Ministry, operates just a few miles from Temple Square, the Salt Lake City complex at the heart of the faith.

Steve Shaw, a political scientist at Northwest Nazarene University and co-author of "The Presidents and Their Faith," compares this election to the 1960 campaign of John F. Kennedy, who confronted religious bias to become the first Roman Catholic president. Kennedy’s election marked a move for Catholics more firmly into the American mainstream, a potential shift for Mormons as well in 2012.