I was glad to see W. Jason Wallace receive attention from the Historical Society’s blog. Wallace is the author of Catholics, Slaveholders, and the Dilemma of American Evangelicalism, 1835–1860 (Notre Dame University Press, 2010), a book that triangulates the politics of northern evangelical anti-slavery proponents, southern evangelical defenders of slavery, and apologists for Roman Catholicism against anti-Catholicism.
I recommend the book and also the interview which includes the following nugget:
Over the course of the mid-nineteenth century the Protestant theological divisions of the past came to matter less than how Christianity translated into social and political questions. Evangelicals, however, faced a serious problem when they began to disagree about what constituted legitimate social concerns. Nowhere was this problem more pronounced than with the slavery question. Where theology could be either ignored or debated without real public consequence, politics could not. Antebellum politics betrayed the appearance of unity evangelicals so desperately desired. Both northern and southern evangelicals held fast to the notion that there was in fact a relationship between Protestant Christianity and good government. This relationship, though never explicitly defined, divided millions of evangelicals when the slavery question could no longer be ignored. Northern evangelicals believed slavery to be as incompatible with American values as Catholicism, and they launched a semi-coordinated campaign against both Catholics and slaveholders in sermons, speeches, and journal articles. A consequence of this campaign was that slaveholders, like Catholics, shared the position of the northern evangelical ideological “other”—the outsider who had to be assimilated or reconstructed. While southern theologians retreated into a myopic defense of the peculiar institution, Northern evangelicals increasingly allowed their understanding of the church to be defined by the American experiment.
The lesson appears to be that when you make a religious defense of a particular political order a habit, politics wind up swallowing your religion. Americanism is and was as much a problem for Protestants as it was for Roman Catholics in the United States.