Distant Ocean has the goods.
A serious effort to teach lessons presupposes an ability to learn. Incorrigibly stupid people can't learn. Neither can solipsists, psychopaths or Democrats, who routinely manage to combine all three qualities. I wouldn't waste my time on them. A spite vote has some passing appeal, but they read every vote the way they want to, regardless of intent. In short, as a method of signaling or teaching, there's no point to voting.
There is, however, something to be said for a "third party" vote that gives Robert Parry a full blown conniption. A bit silly? Sure, but I'm not so morally vain that I'd pass. There's also a tiny chance a genuinely decent person will sneak into some office or another and, once there, do a few, small, genuinely decent things. It's a wisp, admittedly, hardly the stuff of which revolutions are made, but at the very worst a vote for a good person is a respectful gesture. The Democratic purists may wish to foul themselves and run around shrieking for attention over that, but that's what they do anyway. And if my inbox is any indication of what portends, they're winding themselves up for another irredentist tantrum. Their tantrums make the Baby Jesus cry. That's a bad thing. There's nothing I can do about it, sadly, but it's also no reason to spite my "third party" friends.
I'm almost, but not quite, tempted to vote for the Republicans. The last time they had an electoral majority, Democratic Party supporters, though not the Democrats themselves, felt obliged to offer nuisance value opposition to Cat Food Commissions, bankster-coddling and crackpot hegemony. They didn't really mean it, but some of them were panicked enough to act like grownups. That's good practice, according to the developmental enthusiasts. It can become habitual and, eventually, thoughtful. But even in a very good cause, there are limits. No matter how much I'd like to see grownup Democratic Party supporters, I can't stomach the aggrieved triumphalism of Republicans. Where it's possible, I'll hug a meliorist instead.