Today, by contrast, progressive white candidates more often cite religion as a source of division. In his announcement video, O’Rourke boasted that during his Senate campaign in Texas, “people allowed no difference, however great or however small, to stand between them and divide us. Whether it was religion or gender or geography or income, we put our labels and our differences aside.” The only reference to faith in Warren’s announcement speech was an acknowledgment that “we come from different backgrounds. Different religions.” The lone reference in Sanders’s was a call for “ending religious bigotry.” While white progressives once described religion as something that brought Americans together, they’re now more likely to describe it as something that drives them apart.

It’s not hard to understand why. For starters, the percentage of white Democrats who express no religious affiliation has skyrocketed. According to unpublished data tabulated for me last year by the Public Religion Research Institute (PRRI), 8 percent of white Democrats expressed no religious affiliation in 1990. By 2016, the figure was 33 percent. In 1990, white self-described liberals were 39 points more likely to describe themselves as Protestant than as religiously unaffiliated. By 2016, religiously unaffiliated beat Protestant by nine points.

Secular Democrats haven’t only grown more numerous. They’ve also become some of the party’s most motivated activists.