This straightforward view that Christian political life simply was a manifestation of inner virtue came under severe attack with the Protestant Reformation, in part because of the (often legitimate) claim that medieval structures of political power had failed massively in their aspirations to such goods, becoming instead systems of control and exploitation. Protestants argued that rather than pursuing virtue and power in tandem as the medievals had done, the two should be handled separately.
The American project itself, and its large evangelical population in particular, have always been descendants of this critique of the falsity of Catholic piety. The initial suspicion that many monks were using their aura of spirituality just to accrue power became a wholesale critique of the idea that virtue and power could ever coincide. (Think of Lord Acton’s famous maxim: “Power tends to corrupt and absolute power corrupts absolutely.”) Once the organic link between virtue and power is severed, however, the relationship between the public and private becomes deeply unstable. Such instability has been manifest in America, and in American low Protestantism from the start, as different values vie for primacy.