After the grinding pessimism of my previous post, I think it rather behoves me to also look at the question, what can we do, and specifically for this audience, what's the role of the historian in this? I'm much less certain I have any answers here, but I have some thoughts so I thought I would put them up to be shot at.
I suspect, myself, that the morally correct response for the committed democrat in a situation like this is to quit his or her job, whatever it may be, start and then manage and fund-raise for a new party eschewing the principles they'd actually like to see mattering in politics. It wouldn't work, probably, but it would be ethical, and I honestly think that's what I should do. But I really really don't want to, I want to pay someone else to run the country for me so I can get on with my research, which is what I'm actually passionate about. So hopefully there is a rôle for a historian in this, right?