Replacement theory in America has domestic antecedents much older than Renaud Camus and Jean Raspail. Henry Ford, among other Americans, promoted “The Protocols of the Elders of Zion,” which — through an entirely fictional depiction of a powerful Jewish conspiracy that controlled world events — has influenced racist theories and beliefs from its initial publication in the early 20th century. Worries about the body politic and threats to the racial composition of the nation inspired eugenics campaigns, anti-immigration activists, and other Progressives, including Theodore Roosevelt. These ideas have been braided with environmentalism not only by ecofascists in the recent past,...