The thing is, I’ve often seen people express an opinion of how can blacks or gays vote Republican. It’s even been expressed here in this thread. I am neither, but I can imagine plenty of scenarios where that might happen. Consider that just because someone is black or gay may not necessarily be as important of an issue to them as other issues.
For example, imagine a gay man who has been in a committed relationship with his partner for some time and is interested in getting married, and for the sake of this example, let’s assume it’s before the recent SCOTUS decision. Let’s also assume that he has other issues he cares about, like perhaps he happens to agree with the general Republican economic and foreign policy, maybe he’s pro-gun, whatever. Of course, he’s upset that many of the leaders of the party are preventing him from getting married, and he’s working hard to change those opinions. But he’s faced with a dilemma. Does he vote with the party that agrees with the majority of his opinions but will continue to fight against marriage equality, or does he vote Democrat just for that sake?
Perhaps he thinks about this long and hard, and realizes that, though he wants to get married, he’s well enough off that the financial aspects of marriage aren’t a big deal, and their wills are in order, and their friends and family all support those decisions. He’s certainly not concerned his partner is going anywhere either. Perhaps he sees that the tide is turning on this and he can continue to work within the party and in other causes to effect social change and win that right at some point in the future. So he decides that he’ll have to concede that point and vote what he thinks is ultimately best.
Many would accuse him of voting against his own self-interest, because Republicans hate gays. And while this is a bit of an extreme example, I do think it’s quite unlikely that most people have a candidate that they agree with on EVERY point. So, to a certain extent, we’re ALL voting against our best interest in at least some fashion, but ultimately we’re either voting for our own best interest overall, or maybe even what they hope is in the country’s or the world’s best interest.
Now, sure, maybe we could make an argument about people that get misled, as in people saying the poor are voting for Republicans, or clearly the rich that vote Democratic have ulterior motives. But even if you’re actually right about that, it’s not like they’re knowingly going into the booths to screw themselves over. Politicians misrepresent and lie about stuff all the time, some bigger and more often than others, but they’re still voting in what they believe is their interest, they’re just wrong about it.