I've voted for Democrats all of my life, as well.  I don't know what to say to the people who vote against their interests.  Part of the problem, as I see it, is that there are heavily financed forces that use every trick in the book to convince people to do so.  They use racism, xenophobia, homophobia, misogyny and anything else that works.  I don't know if there is a way to turn the majority of the population into thoughtful, discerning voters, who do the hard work of really becoming acquainted with the issues and with positions and who think all of this through.  The fact that many can be manipulated is why demagogues have had such successes.