The “spiritual but not religious” Bill de Blasio could sure use a unique appeal. Photo: Sean Rayford/Getty Images

It’s been obvious for a good while that the fastest-growing religious category of Americans is “none” and that the politically engaged irreligious are to a significant extent consolidating in the Democratic Party. Both trends are being reinforced by the religious and political proclivities of millennials and post-millennials.

So irreligious Democrats are hardly a marginal phenomenon these days. As Amelia Thomas-Deveaux observes: “People who identify as atheists, agnostics or ‘nothing in particular’ accounted for 35 percent of Democratic primary voters in 2016, according to the Cooperative Congressional Election Study.”

You’d think, then, that with a 2020 Democratic presidential field of 23 candidates — so numerous that when they gather in the same place, you can’t stir ’em with a stick — someone would find a comparative advantage in appealing to these people. As it stands, Bernie Sanders appears to be doing well in this demographic by coincidence and default:

[A]ccording to crosstabs from Morning Consult’s weekly tracking poll for May 20–26, support for Sen. Bernie Sanders is higher among religiously unaffiliated voters than among religiously affiliated voters …

Yes, Sanders is a political rarity because of the openness with which he’s spoken about his lack of faith, but why are nonreligious voters more drawn to him?

Thomas-Deveaux notes that “very liberal” and young voters are more likely than others to be secular-minded, and those are Sanders strongholds. But it’s also possible that nobody’s bothering to compete with him more directly on this front:

Sanders also may be drawing on a little-tapped well of secular enthusiasm on the left, particularly among atheists and agnostics. “Their nonreligion may not be the driving factor for their support for Sanders, but it’s very likely a contributing factor,” said David Campbell, a political science professor at Notre Dame University who studies religion and civic life. His research has found that a significant share of Democratic Party activists don’t just lack a religious affiliation, they have actively embraced a secular worldview — and political arguments rooted in socioeconomic justice might resonate especially with them. Nonreligious voters might, too, see their own identity reflected in Sanders’ lack of overt religiosity, which could add to his appeal. But there’s also room, Campbell said, for candidates to reach atheists and agnostics even more directly. “This is a big group of voters who usually get ignored,” he said. “One way to stand out from the pack is to try to explicitly address them in secular terms.”

Could that yet happen if a churchless candidate looks at the data and figures that he or she could survive (even at the risk of becoming less electable in the general election) by drawing some attention to his or her lack of religiosity? Well, politics abhors a vacuum, and this could be one. The only overtly religious Democrats in the 2020 race are, arguably, Pete Buttigieg, Cory Booker, and (in a less orthodox but more pervasive sense) Marianne Williamson. Elizabeth Warren has a pretty solid history of religiously informed civic and political engagement, though she doesn’t talk about it much. So does Andrew Yang. Joe Biden’s Catholicism is important to his whole Rust Belt, white working-class appeal. Fellow Catholics Kirsten Gillibrand, Julián Castro, Tim Ryan, Beto O’Rourke, and John Delaney aren’t going to repudiate their heritage even though they disagree often with the bishops and the Vatican. Kamala Harris will likely emphasize her identification with the African-American church as she pursues black voters in the primaries. Amy Klobuchar is a reasonably observant mainline Protestant, and John Hickenlooper has said he tries to live by the values of his Quaker upbringing. Tulsi Gabbard probably couldn’t escape her Hindu affiliation even if she wanted to.

Candidates whose religious views are so indistinct as to be invisible (at least in terms of the 2020 race) include Steve Bullock (a onetime Catholic), Michael Bennet (the product of Jewish and Christian family influences but not apparently observant), Seth Moulton and Eric Swalwell (whose official affiliations according to Pew are “unspecified Protestant”), and presumably Wayne Messam (whose sparse press clips don’t mention religion).

The 2020 candidate, however, who has been most conspicuously non-religious may be New York’s own Bill de Blasio, as Jeff Cotlin observed last year:

[De Blasio] identifies as spiritual, not religious, and does not belong to any church.

De Blasio’s press secretary Eric Phillips told City & State the mayor’s lack of a church has never been an issue with voters. Opposition messaging blaring from vans in the 2013 campaign deriding him as “anti-church” and atheistic didn’t seem to hinder his landslide win. Since a handful of articles following his 2014 inauguration discussed his (lack of) religious views, the mayor’s beliefs have been largely ignored in the media.

That’s typically what irreligious pols have hoped would happen. But maybe de Blasio is missing his main chance to turn his much-ridiculed campaign into something nationally noteworthy: He could be the loud-and-proud candidate of the religiously unaffiliated, including the conflicted, the spiritually indifferent, the proudly godless, and the self- (or television-) shepherded.

If not in 2020, it will happen someday soon.