The question is especially relevant with respect to evangelical Protestants, for three reasons. First, in sheer numbers they are the largest group in the Republican coalition, as defined by church affiliation. Second, they tend to be quite active during the primary season and can influence outcomes, especially in the South where they are most numerous. Third, while no Christian body accepts a Mormon baptism as valid, evangelicals have tended to be more critical of Latter-day Saints doctrine than mainline Protestants or Catholics, with some evangelicals (and more fundamentalists) labeling the church a "cult." Millet says that "the greatest tension" has been with evangelicals, who have written "most all of the anti-Mormon stuff."

What do evangelical leaders active in politically conservative circles say about a Romney candidacy? Many I asked were reluctant to be quoted by name. As one of them told me, "We have to work with Mormons." Over the past quarter-century Mormons have made common cause with politically conservative evangelicals (and Catholics) on a broad range of issues involving marriage, family, abortion, stem cells, pornography and religious liberty. Moreover, Mormons have worked alongside evangelicals for many of the same candidates at election time.

Someone willing to go on the record was Charles Colson of Prison Fellowship. Notwithstanding his "fundamental" theological differences with Mormonism, Colson said, "I could in very good conscience support Romney," calling him "a first-rate guy in every respect" and "a social conservative on most of the issues we care about." Colson obviously wasn't declaring for Romney but simply indicating that he would not in religious principle, so to speak, be opposed to Romney and indeed could find political reasons to support him. Whether he would actually do so, of course, would "all depend on what the lineup is" and "where each person stands."

The other evangelical leaders I contacted took the same view. Colson offered the likely correct forecast: Romney's appeal to evangelicals might slacken if a competent evangelical or Catholic with social views similar to Romney's were in the race; on the other hand, Romney's stock with evangelicals might go up if he were pitted against candidates holding more liberal social views, regardless of their religion. One evangelical leader offered this succinct take on whether Romney's faith would hurt him in the primaries: "Against Giuliani, no. Against Frist, yes. Against (Rick) Santorum, yes. Against Arnold (Schwarzenegger, who is ineligible), no."

Romney's positions on social issues could make or break his candidacy, and social conservatives who've followed his term as governor tend to give him mixed, though on balance positive, reviews. He's generally praised for his stand against same-sex marriage, though some conservatives think he could have used his executive powers to prevent the implementation of the state Supreme Court's decision affirming such unions. He's applauded as well for opposing the creation of embryos for research. But he's drawn criticism because he would allow research using "surplus" embryos created through in-vitro fertilization.