In October of last year, Josh Mandel, a candidate in Ohio’s Republican primary for the state’s open U.S. Senate seat, insisted during a debate that “there’s no such thing as separation of church and state.” Three months later, Supreme Court Justice Neil Gorsuch made an off-hand reference to the “so-called separation of … church and state” during oral arguments.

In April, Pennsylvania gubernatorial primary candidate Doug Mastriano, now the Republican nominee, dismissed the separation of church and state as a “myth.” 

By June, Colorado Rep. Lauren Boebert, speaking at a Colorado church, proclaimed, “I’m tired of the separation of church and state junk that’s not in the Constitution. It was in a stinking letter, and it means nothing like what they say it does.”

The growing popularity of these kinds of declarations is striking given the place the separation of church and state has occupied in American politics going back to the Founding Fathers. Though the phrase “separation of church and state” does not appear in the U.S. Constitution, the notion is deeply rooted in American jurisprudence and popular culture.

More immediately, the rhetoric has alarmed some Americans who associate the constitutional debate over the church-state split with extreme versions of Christian nationalism.

Yet, antipathy toward the separation of church and state among conservatives is not new but, rather, is a decades-old argument popularized primarily by a controversial Texas activist in the early ’90s, when the religious right was ascendant.

In 1993, the Rev. Jerry Falwell Sr., founder of Liberty University and co-founder of the Moral Majority, promoted a book called “The Myth of Separation” by a Texan named David Barton. According to a Christian Century report, less than a month later on Falwell’s television show, “The Old Time Gospel Hour,” he preached a strident sermon in which he said, “Let everyone know that this separation of church and state business is bogus.”

In 1988, Barton, a self-taught historian and activist, had founded WallBuilders, a group dedicated to “presenting America’s forgotten history and heroes, with an emphasis on the moral, religious, and constitutional foundation on which America was built.”

The organization has dutifully forwarded Barton’s Christian vision of American history ever since, serving as a one-stop shop for his books, videos and materials. It has consistently taught that the separation of church and state is a modern fabrication.

While Barton was not necessarily the first to make the claim, Kristin Kobes Du Mez, a historian and professor of history at Calvin University, said Barton is “extremely influential in evangelical spaces, and has been for decades.”