“Here, in the United States, we are alarmed by new calls to adopt socialism in our country,” Donald Trump said in his State of the Union speech, adding that, “Tonight, we renew our resolve that America will never be a socialist country.”

It was just the latest in a new swell of anti-socialist talk on the right. In October, the president’s Council of Economic Advisors released a report on “the opportunity cost of socialism.” In the months since the midterms, the right has grown increasingly obsessed with Alexandria Ocasio-Cortez and her democratic socialism. It seems increasingly likely that the theme of the 2020 election will be a full-on red scare. 

There is a term for this, of course: red-baiting, a fixture of American politics for much of the 20th century. I spoke to Kathryn Olmstead, professor of history at the University of California, Davis, and author of Right Out of California: The 1930s and the Big Business Roots of Modern Conservatism, about some of that history. Our conversation has been lightly edited for clarity and length.