Political consultants love to speak of a candidate’s supposed liabilities’ having been “vetted” in a prior campaign. It is an article of faith in political circles that once a candidate successfully runs the gantlet of a potential charge, he or she will never have to revisit the matter. As an example, George Bush in 2004 didn’t have to answer as many questions about youthful indiscretions as he did in 2000.

There is a corollary to the vetting rule, however, and it is terribly important for the future presidential prospects of Massachusetts Gov. Mitt Romney. The corollary says that the vetting effect works only for the same office. If a candidate runs for a different office, particularly a higher office, any charge may have to be vetted all over again.

The mountain that Romney will have to climb a second time is his Mormon faith. That may strike Romney and his backers as unfair, but it’s certain to be necessary. If he has any doubts, he should just check in with fellow Mormon Sen. Orrin Hatch (R-Utah).

Hatch, of course, ran for president in the 2000 election cycle. When the senator started that race, he was relaxed about his faith and suggested that he looked forward to opportunities to correct misperceptions about the Mormon church, the Church of Jesus Christ of Latter-day Saints. A poll taken at the time suggested that almost 2 in 10 Americans wouldn’t vote for a Mormon. Hatch cheerily responded that he’d campaign for the votes of the 8 in 10 who weren’t so prejudiced.

After he’d experienced the slings and arrows of campaigning in Iowa and other states, he lost some of his graciousness. Implying that prejudice was stronger than he had realized, Hatch popped off, saying, “I am not going to take any crap from anybody about my religion.” The charge that seemed to irritate Hatch the most was that Mormons are not Christians. “I take my Christian faith very seriously,” protested the annoyed candidate.

Two nationwide surveys of Protestant ministers add some context to Hatch’s experience.

A 2000 national survey by Ellison Research of 518 Protestant ministers found that 63 percent would vote for a Jewish candidate and 64 percent would vote for a Catholic but 76 percent confessed that they would be less inclined to vote for a Mormon candidate.

A Mormon-sponsored 2001 survey of non-Mormon clergy in Utah and California revealed that 78 percent would not classify Mormons as Christians. The survey found that these ministers mostly characterized Mormons as “well-meaning, but misguided.” About 1 in 3 of the pastors described Mormons as “non-Christian cultists.”

That Romney successfully overcame Massachusetts Democrats’ clumsy efforts to brand him a cultist in his unsuccessful 1994 Senate race and winning 2002 gubernatorial bid has no bearing on the issue’s relevance in 2008.

First, the presidency is an office that inspires the closest scrutiny. Everything gets studied and restudied, especially if it provides an insight into a candidate’s values. Second, several odd policy positions taken by Mormons recently — Hatch’s pro-stem-cell posture and Romney’s moderated views about abortion and civil unions — will cause some conservatives to take a second look at Mormon theology and belief. And third, the Republican primary trail winds through Southern states where people know their comparative religions.

Whereas few ordinary Northeastern Catholics were apt to ponder the theological meaning of an unfamiliar “cult,” Romney will encounter numerous lay Southern Baptists, Methodists and myriad lesser-known evangelical adherents who will sportingly probe his family’s faith. They can knowledgably question the purported polytheistic beliefs of Mormonism or its unconventional views about Scripture canon. If Romney, like Hatch, has two favorite Scripture passages, one from the holy Bible and another from the Book of Mormon, he can expect trouble in the Bible Belt.

In any event, the photogenic Romney’s nonsmoking, nondrinking, non-cursing persona will win an audience with Christian conservatives. How he handles that encounter will make or break his candidacy.

Hill is director of Hill Research Consultants, a Texas-based firm that has polled for GOP candidates and causes since 1988.