The phrase “political religion” comes from Abraham Lincoln. It appears in a speech he gave on the importance of revering, as if they were sacred documents, the Declaration of Independence and the Constitution. The idea that a healthy state would incorporate religious veneration for its laws and polity was described by Jean-Jacques Rousseau in The Social Contract, and Lincoln was following Rousseau when he used the phrase. Furthermore, a religious sense inheres in the idea that the American experiment in democracy is also a world-historical—and specifically providential— endeavor. This idea became common in the 19th century, linked to the American exceptionalism documented by de Tocqueville.

It’s clear that Lincoln was influenced by these ideas. He saw the Constitution as sacred and the Civil War as necessary to preserve something sacred. Moreover, as Lincoln aged, he became more idiosyncratic in his personal religious convictions, believing that the call of his conscience was, in some real sense, the voice of God, and that moral and spiritual development required principled adherence to that call. For Lincoln, who claims to have always had a natural antipathy to slavery and did consistently express reverent admiration for the founding principles of the American Republic, this call would be heeded and realized—imperfectly—over the course of a contentious political career.