This was a lesson that many evangelicals learned afresh in the 1970s and 1980s, when Catholics spearheaded the pro-life movement in reaction to the 1973 Roe v. Wade decision legalizing abortion. Most evangelicals and Catholics have sharp theological differences over the nature of the church and the way of salvation, yet their agreement on moral issues such as abortion made political cooperation a must. Mormons also became a part of that faith-based alliance, and their questionable doctrines never became an acute political problem until Mitt Romney emerged as a leading candidate for the Republican nomination. (The Mormon issue never seemed as troublesome, by contrast, to the legions of evangelicals who became devoted followers of Glenn Beck in recent years.)

The theological differences between evangelicals and Mormons on issues such as the human potential for divinity, and the history of the church, are deep. Evangelicals should be aware of these differences, and should be willing to speak to Mormon friends about them. But as my fellow Patheos columnist Douglas Baker has argued, evangelicals need to think about politics primarily as an exercise in building alliances for the public good, not as a test of personal doctrine. Evangelicals may well conclude that Mitt Romney is not the most attractive primary candidate because of his relatively suspect record on issues such as the right to life. But refusing to support a candidate simply because of theology is a wrong-headed approach to politics, and an approach that Baptists in early America would not have recognized.