Today’s white liberals don’t only talk about faith less than their predecessors did. They talk about it in a strikingly different way. Earlier Democrats invoked religion as a source of national unity. Bill Clinton declared in his 1992 convention speech, “There is no them; there’s only us. One nation, under God, indivisible, with liberty and justice for all.” In his 2004 convention keynote address, Obama famously announced, “We worship an awesome God in the blue states.” The implication was that religious observance was something Americans of both parties shared.

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 According to unpublished data tabulated for me last year by the Public Religion Research Institute (PRRI), 8 percent of white Democrats expressed no religious affiliation in 1990.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.

Read: Why Democrats must regain the trust of religious voters

Secular Democrats haven’t only grown more numerous. They’ve also become some of the party’s most motivated activists. As The Atlantic’s Emma Green has noted, a PRRI poll taken last August and September found that Democrats who shun organized religion were more than twice as likely to have attended a political rally in the previous year than Democrats who identify with a religious group. Today’s Democratic candidates cannot simply assert, as Obama did in 2004, that “we worship an awesome God in the blue states,” because so many active Democrats do not.

The other reason liberal candidates more often describe religion as a source of division is the rise of Islamophobia and anti-Semitism. Before Donald Trump, Republican religious discourse was more ecumenical. The 2000 Republican convention featured a Muslim prayer, and George W. Bush regularly spoke about Americans who attended a “church, synagogue, or mosque.” In such an environment, it was easier for Democrats to depict an America divided by race, class, and gender but unified by religious faith, even if different Americans expressed that faith in different ways. Today, by contrast, since more Americans don’t practice a religion, and the president demonizes some of those who do, it’s more natural to describe religion as a rift to be overcome.