While other Mormons have held positions of political power, including Senate Democratic Leader Harry Reid of Nevada, none has ever been elected president. Utah Sen. Orrin Hatch, also a Mormon, sought the GOP nomination in 2000, but was quickly eliminated from the race. The possibility of a Mormon president has renewed questions about whether the public in general — and evangelicals in particular — would support a candidate from a faith that the Southern Baptist Convention, the nation's largest Protestant group, considers a cult.

The domination of early Republican primaries and caucuses by social conservatives — generally defined as churchgoers who oppose abortion rights and gay marriage — may explain why Romney has been aggressively recasting himself as a conservative after presenting himself as a moderate while running for governor in 2002.

His challenge was underscored earlier this month when some conservatives questioned the validity of his credentials after learning of a 1994 letter in which Romney — then a candidate for the U.S. Senate — pledged to be more effective in promoting the gay agenda than Sen. Edward M. Kennedy, D-Mass. Kennedy is considered by many on the right to be the most liberal member of Congress.

In his gubernatorial campaign, Romney also pledged to uphold abortion rights in Massachusetts. Today, he says the landmark Roe v. Wade decision legalizing abortion is wrong.

Yet the theology of his religion bodes to be particularly problematic for his presidential candidacy, at least at the outset, experts say.

The Book of Mormon, which church founder Joseph Smith Jr. said he translated from golden plates he discovered through an angel in the 1820s, says that Israelites migrated to the New World and were the ancestors of American Indians. Latter-day Saints also believe that Smith restored authentic Christianity and rewrote parts of the Bible to correct it.

Another Mormon rule that frequently raises eyebrows is the bar on access to their temples by anyone except members of the faith who donate 10 percent of their earnings to the church, who uphold its teachings and who fulfill other duties. Mormons who meet the criteria are given ID cards that they must display to gain admittance.

"There will be some initial apprehension from many conservative Christians who have been taught that Mormonism is a cult," said Rev. Joel Hunter, pastor of the Northland Church in Longwood, Fla.