The democratic party and American leftists no longer understand non-college working people and, for the most part, no longer reach out to them. Working people think that the left today advocates either for weirdos or for the completely screwed up, and wants everybody to pay for its programs to help said weirdos and fuckups. There is some valid reason for this impression, with the Great Society programs and affirmative action in the sixties and seventies being partly funded by taxes on the middle classes, along with fiascos like school bussing and over-compensated hiring practices screwing over people who didn't feel like they deserved it. (And poor management of government agencies making them ineffective at cost effective delivery of services.)
However, working people don't see themselves as fuckups (because they're not), and they don't have a lot of patience with weirdos. So they aren't going to feel comfortable with the gay marriage/ social worker part of the left (the old union guys were socially very conservative for the most part).
Also, most of the left today seems to me to be made up of people who really have no connection to actual poor working class people, so there is automatically a divide that is mobilized by the Karl Roves of the world.
Furthermore, if you have ever been lower middle class or "working poor", you learn early that very traditional personal character values can make the difference between you and your family living in a truly shitty situation or rising out of the muck around you to actually have a decent marriage/ nice friends/ safe home. So when college educated lefties come around and tell them to have pity on fuckups and weirdos because its society's fault, or that personal character and traditional values don't matter, any working class person is likely to tell them to go to hell.
So today's Republicans mobilize personal character rhetoric, traditionalism rhetoric, and the cultural non-understanding between leftist leadership and working people, and -- voila, working people voting against their own interests.
Until the left figures out the working classes again -- which means taking the time to show up in the middle of the country, go to church, eat ribs, etc, etc -- Capital will continue to screw everyone. So quit whining about how stupid working class people are -- nobody represents their interests today, neither left nor right, but at least the Republicans pretend.