That’s a particularly tasty bit from the new Pew poll on religious views in America, always one of the richest cultural surveys of the year. Two caveats, though. One: “Unaffiliated” is not a synonym for “agnostic” or “atheist.” Most people who call themselves “unaffiliated” believe in God. The word means just what it says, that the person doesn’t adhere to any one faith at the moment. Two: “Unaffiliated” is the largest Democratic religious demographic only if you divide Christianity among its component groups, i.e. Catholics, mainline Protestants, evangelical Protests, historically black Protestants, and others. As a group, Democrats are still overwhelmingly Christian at 63 percent.

But give ’em a few decades.

Actually, given the trend line there, “a few decades” may be more than they need. The percentage of Christians is down double digits in just seven years; at that rate, they’ll be a minority circa 2025-30. As for Republicans, the share of “unaffiliated” within the party has also grown — but only by four percent since 2007. The biggest religious group in the GOP remains evangelicals at 38 percent.

I think the change is less a function of older, more traditionally religious voters losing faith than them dying off and being replaced by millennials, who are more likely to be Democrats, more likely to be religiously “unaffiliated,” and less likely to be believers in the first place. Check out these numbers, especially the last line:

They haven’t given up on God but an awful lot of them have given up on religion as a meaningful influence in their lives. That’s the flip side of being “unaffiliated”: Just as there are many people who don’t belong to any one religion but continue to believe in God, there are also many who do nominally subscribe to a religion but don’t consider it important to their life day to day. In fact, here’s the change from 2007 to 2014 when people are asked how significant their faith is to them:

It’s also true that, although most “unaffiliateds” are still believers, the share of the group that says religion isn’t important to their lives is growing, from an estimated 21 million in 2007 to 36 million now. In other words, people who belong to a faith are losing ground to those who don’t, and among those who don’t, those who think belief is important are losing ground to those who don’t.

Maybe this is just self-sorting amid a key cultural change. As the social taboo against being non-religious or even atheist weakens, more people who belong to a church mainly out of habit might feel freer to redefine themselves. In that case, we’d expect to see not only more people calling themselves “unaffiliated” and more unaffiliateds professing that they don’t believe in God at all, but maybe also a greater percentage among people who do still identify as members of a faith claiming greater devotion. In other words, once the weak believers within a faith break free, what’s left should be a greater concentration of strong believers. And that is what we see here. Among unaffiliateds, those who say they don’t believe in God or a spirit has increased from 22 percent in 2007 to 33 percent today. And among those who are affiliated, a greater share are practicing their faith more diligently:

Seems like we’re headed towards churches growing more slowly or even losing members, but also towards congregations that are more uniformly devout. Polarization between the affiliated and unaffiliateds, in other words. What else is new?

Here’s a classic moment from the last Democratic convention when the party tried to amend the platform to reinsert the word “God.” Didn’t go so well. It’ll go less well in the future, and eventually they’ll drop that language entirely.