I said this (ineloquently) on the podcast, Micah, but I agree with you that a lot can just be chalked up to human nature — and, therefore, you can’t easily separate my “it’s all macro trends!” from Nate’s “what are the real-world reasons?”
It’s virtually impossible for a government to do everything well, and because the grass is always greener on the other side, voters (and, to be honest, the media) will fixate on the stuff that isn’t going well, and that becomes the reason (or excuse, if you like) why voters turn against the party in power. Right now, it might be the delta variant; it might be the sluggish economy; it might be lack of action in Congress. But whatever it is, it’s scratching an itch that is inevitably going to be there.