This is likely mostly black people.

Working-class (as opposed to underclass) black people are actually quite socially conservative. You kind of have to be when you have that underclass right next to you. They all vote D anyway, the unspoken agreement between the Ds and the minorities is that they'll leave the non-whites to live their lives, and not come trans their kids, to reserve that stuff for the whites. Obama being black himself likely raised the turnout.

But if you go and ask them what they think about gay marriage, they'll tell you.