ALMOST A CENTURY AGO, IN THE AFTERMATH OF the First World War, the journalist Walter Lippmann, then 32 years old, published an influential and disturbing critique of democracy and its future. The mood in the U.S. was anxious—about immigration, about race, about women, about the nation’s role in the world, about civil liberties, about religion, even about science (the Scopes trial was a few years off). The 1920 Census had found that more Americans now lived in cities than on farms, and the broad introduction of commercial radio at around the same time was reshaping the nation’s media landscape; such forces had helped lead to the founding of a second, widely popular Ku Klux Klan—a movement designed to protect Anglo-Saxon superiority in the face of shifting demographic trends. It was,…