Mainstream scholars disagree, sometimes vehemently. Randall Balmer, a professor of American religious history at Barnard College and writer of the documentary “Crusade: The Life of Billy Graham,” told me: “David Barton has been out there spreading this lie, frankly, that the founders intended America to be a Christian nation. He’s been very effective. But the logic is utterly screwy. He says the phrase ‘separation of church and state’ is not in the Constitution. He’s right about that. But to make that argument work you would have to argue that the phrase is not an accurate summation of the First Amendment. And Thomas Jefferson, who penned it, thought it was.”