America is at risk of descending into authoritarian nihilism. The playbook is familiar. A regime comes to power with as genuine a popular imprimatur as one can expect in modern liberal democracies. It uses small kernels of truth in its critique of the existing liberal order to underwrite claims of a total revolution. It uses an “odd pimple or two as an argument for cutting off the whole face”, as one wit, inelegantly but effectively, put it. It uses the form and structures of that very democracy to subvert the basic spirit of liberal democracy. It is authoritarian in its...