IIn 1791, America built a wall. The First Amendment forbade the establishment of a state religion and protected religious freedom. Thomas Jefferson called it the “wall of separation of church and state.” But there have always been cracks. Since the founding of the Republic, Christianity has been the majority religion, and many Christians have felt obligated to bring their faith into politics. According to the nonprofit Public Religion Research Institute, more and more Americans say they have no religion, but nearly two-thirds are Christian. In the 1980s, white Christians, especially “born-again” evangelicals, emerged as a strong Republican voting bloc. According to a Pew Research Center survey, 60% of Protestants (and 81% of white evangelicals) plan to vote for Donald Trump in the November presidential election. Here are four books and podcasts that explain the relationship between politics and Christianity in America.