"It would have been infinitely better had he been able to go to the Values Voters Summit with the speech already given," said Ralph Reed, the former executive director of the Christian Coalition.

Tom Minnery, the political director of Focus on the Family, an evangelical organization in Colorado Springs, Colorado, said Romney has "allayed some fears" about his religion by showing he didn't turn "the governor's mansion in Massachusetts into a Mormon temple."

Yet for conference-goers such as Noah Crowe, a Southern Baptist pastor from Robbinsville, North Carolina, there's nothing Romney can do to overcome their distrust of Mormonism. "His faith is not the faith I believe in, teach and preach," said Crowe, who added that he studied Mormonism at his Bible college in a course called "Cults and False Religions."

For evangelicals, many of whom believe the Bible is the literal word of God, the Mormons' founding text, the "Book of Mormon," makes it impossible for them to be considered Christians, according to Fred Smith, associate professor of Theology at Liberty University in Lynchburg, Virginia.

"We believe the Bible and the Bible alone is the final authority," Smith said.

The Mormon faith was established in 1827 by Joseph Smith Jr., who claimed to have discovered the Book of Mormon engraved on golden plates buried near his house in western New York. The text asserts that American Indians are descended from a lost tribe of Jews who arrived in the Americas around 600 B.C., and that the Garden of Eden was in Jackson County, Missouri.

Those beginnings sound "farcical to most Americans," said Brett Clifton, a professor of public policy at Brown University in Providence, Rhode Island.

Romney's supporters argue that he doesn't need to address all of the tenets of Mormonism to make his case to evangelical voters. "Talking about values is a winner, talking about theological stuff is a no-no," said Representative Tom Feeney of Florida, a Republican who backs Romney.

Richard Land, a leader of the 16 million-member Southern Baptist Convention, disagrees. Romney, he says, has a lot more explaining to do. "When he goes around and says Jesus Christ is my Lord and savior, he ticks off at least half the evangelicals," Land said. "He's picking a fight he's going to lose."