A few weeks ago, the Democratic National Committee formally acknowledged what has been evident for quite some time: Nonreligious voters are a critical part of the party’s base. In a one-page resolution passed at its annual summer meeting, the DNC called on Democratic politicians to recognize and celebrate the contributions of nonreligious Americans, who make up one-third of Democrats. In response, Robert Jeffress, a Dallas pastor with close ties to Trump, appeared on Fox News, saying the Democrats were finally admitting they are a “godless party.”This was hardly a new argument. Conservative Christian leaders have been repeating some version of this claim for years, and have...