They’re not the only group still opposed, of course — senior citizens and white evangelicals also say no to SSM — but they’re the only group that’s under intense partisan pressure to conform that’s still resisting. When Obama announced his support for gay marriage in 2012, at least one poll showed a sea change in black opinion in the aftermath, from 41 percent in favor to 59 percent virtually overnight. One 2012 exit poll found 51 percent support for SSM among blacks versus 41 percent opposition. Pew’s polls over the years have found that black support did increase noticeably between 2010 and 2012, possibly driven by O’s friendlier rhetoric towards SSM or possibly by the broader national trend in favor, but over the past few years that support has leveled off. As things stand today, the closest thing to the GOP’s socially conservative base on gay marriage outside the base itself is blacks.

Makes me wonder how the numbers will look after the Supreme Court legalizes the practice. Will blacks come around, with Democratic Party leaders celebrating the decision euphorically, or is this opposition durable?

Black support has increased 14 points in the past 10 years, but to put that in perspective, support among Democrats aged 70 or older has increased 23 points over the same period. (A majority of Democrats in all four major age demographics now back SSM.) Black Democrats are even more resistant to the social trend than septuagenarians. What’s driving it, unsurprisingly, appears to be religion. Just 33 percent of black Protestants support gay marriage; among white evangelicals, the group that’s most strongly opposed, that number is 27 percent. And the similarities don’t end there:

The only religious groups polled where 40 percent or more see a conflict between SSM and their beliefs are white evangelicals and black Protestants. When you ask people whether gays are born that way or choose to live that way, only three demographics polled reach 60 percent among those who say “choose” — white evangelicals, blacks, and black Protestants. When you ask the same groups if homosexuality is something that can be changed, only three groups reach 50 percent in saying that it can. Guess which three. And when you ask if they’d be upset to learn that their son or daughter was gay, only two groups reach 60 percent who say they would be. Again: White evangelicals and black Protestants. Fifty-eight percent of blacks generally say they’d be upset, almost identical to the 59 percent of Republicans who say so.

Like I say, it’s an open question how much black numbers will change and how quickly, although there are lots of cultural forces pushing them towards the pro-SSM position. Part of it, as noted, is partisan pressure: Democrats will quietly tolerate widespread anti-SSM sentiment among black voters given how important they are to the coalition, but any black pol with national ambitions will have to side with the left on this. As more big-name black Democrats make the switch, presumably more black voters will too. A Supreme Court ruling in favor of gay marriage could legitimize it in the eyes of some skeptics as well. And if it’s true that America’s younger generations are more secular than older ones, and it’s also true that secularists tend to be more comfortable with gay marriage than religious believers, then presumably blacks will trend pro-SSM as less religious younger black voters replace more religious older ones in the electorate. But who knows? Given the hurricane-force cultural winds that Americans have dealt with over the last 10 years, it could be that most of the movement on this issue that’s going to happen in the medium-term has already happened. Maybe blacks, along with their unlikely partners in the GOP base, will be the last bulwarks against SSM for the next decade or two.