Updated

A new survey shows that Americans like their presidents to have faith, and a faith more or less like their own.

The American Values Survey from the Public Religion Research Institute (PRRI) showed that some two thirds (67 percent) of respondents said that it is either very important (39 percent) or somewhat important (28 percent) that candidates have a strong faith.

But nearly one in five (19 percent) said they were less likely to vote for a candidate who had strong religious beliefs different from their own.

The survey results revealed some good and bad news for the two Mormon GOP presidential hopefuls, Mitt Romney and John Huntsman, whose faith has been a source of heated debate among Evangelicals.

Fifty-three percent of those surveyed said they would feel somewhat or very comfortable with a Mormon as president, compared to 42 percent who said they would feel somewhat or very uncomfortable.

By party, though, more Democrats feel uncomfortable with a Mormon as president than Republicans or independents -- Democrats at 50 percent, Republicans at 36 percent and independents at 38 percent.

But the survey also shows that Romney has a growing problem among white Evangelicals, who make up a large chunk of the Republican Party. As knowledge about Romney's Mormon faith increased, his favorability rating among them decreased.

In September, 63 percent of white Evangelicals felt favorably toward Romney. In October, that number dropped to 49 percent, less than half.

In the weeks between those two numbers, a prominent minister opened the floodgates of controversy when he equated Mormonism with a cult. The Rev. Robert Jeffress, senior pastor at First Baptist Dallas, made the comments during the Value Voters Summit in Washington, D.C. His theological definition unleashed a torrent of blogs and articles discussing the doctrinal differences and similarities between traditional Christianity and Mormons' Church of Jesus Christ of Latter Day Saints. What made it even more controversial is that Jeffress endorsed Gov. Rick Perry, a favorite among white Evangelical voters.

But what the survey shows overall, says Robert P. Jones, PRRI director, is that "Romney has a primary problem."

And the problem lies in the Iowa Caucus, the first contest on the road to the White House. In Iowa, says Jones, "white Evangelicals play an outsized role. ... If he gets through the primary, he's good for the general election."

Even though constitutionally there's no religious test to hold the office of president, the survey clearly shows that religion plays a large part in how people vote. The candidates who would have the least chance of winning an election would be those with no religion. Respondents said they were most uncomfortable with a either a Muslim (64 percent) or an atheist (67 percent).