Nothing rounds out the day like a good “America in decline” poll.

I don’t think is evidence of decline per se, of course. I’m not religious myself. But it’s hard not to notice that tribalism, political and otherwise, seems to be expanding as religious identity weakens. And that many of those substitute tribal identities are underwhelming or obnoxious.

If millennials insist upon evangelizing about (a) Jesus, (b) Jordan Peterson, or (c) Ta-Nehisi Coates, which choice is best if (d) none of the above isn’t available?

Fifteen years ago the share of Protestants among the 18-29 group was 34 percent versus 19 percent who had no religion. Today it’s 22/35. The decline in Protestants within the group isn’t purely a function of younger Americans being less religious, though. Young adults are more diverse racially and ethnically so they’re also more likely to include Americans who don’t practice Christianity at all.

Protestants still outnumber the non-religious among Democrats, 36/23, but you can’t understand that number without understanding the racial divide on the question. Black Americans, who are overwhelmingly Democratic, are still solidly Protestant at 61 percent (in fact, they’re the most Protestant demographic group tested here and it isn’t close). White Protestants, meanwhile, are all but vanishing from the Democratic ranks. Blend them together and that’s how you end up with a baseline of 36 percent across the entire party. If you’re white and Protestant these days, odds are very good that you’re a Republican. But even there, the numbers are down. Whereas the GOP was 60 percent Protestant in 2003, it’s 49 percent now. Not even a majority anymore.

A fascinating detail: The rise across the population in non-religious people is basically entirely at the expense of Protestants. Catholics are steady as she goes over 15 years, although there are racial footnotes to that too.

The Catholic share is steady but the demographics are not. Catholicism is also shrinking among whites, as a PRRI survey found last year. The reason the faith isn’t losing ground as a share of all Americans is because the Latino population is growing and Catholicism is the most common faith among Latinos. They also lean Democratic, of course, which means the left is headed (unless it’s already there) towards a party where whites are pretty uniformly secularists, blacks are Protestants, and Latinos are Catholic.

Speaking of which, a sign of the times. I missed it a few weeks ago but there’s now a bona fide secular (i.e. “Freethought”) caucus in the House comprised of four left-wing Democrats. The most outspoken of them, Jared Huffman of California, is a self-professed agnostic, a label that was almost unimaginable among members of Congress a decade ago. It tells you how far left California is, and how much more mainstream the no-religion share of America is, that he feels safe not only embracing the label now but starting a caucus to advocate for secular positions. Makes sense: If this is the direction the wider Democratic Party is headed (or at least the white share of it), it’s going to demand representation.