In the present political climate, the question of whether Mormons are Christians has surfaced again and again. I will leave the issue of whether 21st century America is ready for a Mormon chief executive to pundits, pollsters, and, of course, voters. But the underlying question is an important one, a matter whose implications reach well beyond the 2012 election.

So far as I can determine, the cry of “Mormons are not Christian” was not heard very often during the formative period of Mormon history. Baptists and Methodists and Presbyterians in the area knew that the followers of Joseph Smith believed in doctrinal matters that deviated somewhat from traditional Christianity. Folks seemed to assume, however, that Mormonism fit under the umbrella of...