

What we’re talking about is a game between two players: democrats and their potential voters. It is totally a valid strategy in game theory to punish the other player when they’re not cooperating. If you’re always cooperating even when your opponent (i.e. your preferred political party) isn’t, you’re just encouraging them to continue to not cooperate.
Try out this interactive page.
Yes. Doesn’t mean it’s a bad strategy.
This is not a one-round game. Elections happen repeatedly. If you show someone you will punish them for bad behavior even at cost to yourself, it might teach them to change their ways. On the other hand, always minimizing your losses in the current round (i.e. having no memory or vision) makes you a perfectly predictable and exploitable player.