Once they begin  to circulate, falsehoods—like counterfeit currency—are surprisingly tenacious. It doesn’t matter that there’s no backing for them. The only thing that counts is that people believe they have backing. Then, like bad coins, they turn up again and again.

One counterfeit idea that circulates with frustrating stubbornness is the claim that America was founded as a Christian nation. It’s one of the Christian Right’s mantras and a favorite talking point for televangelists, religious bloggers, born-again authors and lobbyists, and pulpit preachers. Take, for example, the Reverend Peter Marshall. Before his death in 2010, he strove mightily (and loudly) to “restore America to its traditional moral and spiritual foundations,” as his still-active website says, by telling the truth about “America’s Christian heritage.” Or consider WallBuilders, a “national pro-family organization” founded by David Barton, whose mission is “educating the nation concerning the Godly foundation of our country.” Called “America’s historian” by his admirers, Barton is a prolific writer of popular books that spin his Christian version of American history.