People don’t vote against their interests. They vote for their interests as they see them. And right now, working-class and blue-collar whites think the Democratic Party is just implacably against them.
Of course I don’t think it’s true that the Democratic Party is implacably against them. I think they just think the Democratic Party is implacably against them, and part of the reason—not the whole reason, but part of the reason—they think the Democratic Party is implacably against them is that Democratic candidates in red states have no idea how to tell them they’re on their side.
He doesn't discuss the why of this, but the culture wars are surely part of it. It would be easy for a white working or middle class person to conclude (not especially inaccurately) that the modern Democratic party is dominated by an urban elite concerned mainly with advancing the interests of single urban feminists, illegal immigrants, poor blacks, and homosexuals - and almost anybody else, except them. Such is the power of demagoguery, that even the most potent exception is widely reviled, even by those who love the insurance they got thanks to Obamacare but are too deluded to know it.