It is tempting to look for signs of the times in eccentrics and outliers, but ordinary people ultimately make the best bellwethers. I knew the dark, heavy political mood was a real and general phenomenon — that is to say, not limited to those who observe politics for a living — when it caught up with my mom.

Mom is a Texas Republican who's held the same steady non-media job for more than 30 years and has never been especially political. Not that she has no political views; of course she does. But politics has never defined her, nor governed her inner life.

Then came an odd encounter at a Disney Store: While my mother was picking out dolls for my toddler daughter, a bystander got her attention to make a crack about a Pocahontas toy being better called an Elizabeth Warren action figure. It took her a moment to figure out what this stranger was saying; she doesn't follow the news out of D.C. particularly closely.

But then she recalled, dimly, some mud or other that had been slung at some point. After, there was that much less easy contentment in her day, and that much more rumination on the worst parts of American life, which currently seems like a widely shared experience.

The political mood (an anxious, belligerent frustration) is seeping into everything, disrupting moments and exchanges and activities that were formerly peaceful. Conservatives have dismissively labeled it "Trump derangement syndrome," though I think the symptoms are equally distributed among the president's supporters and detractors. Happy people don't bother grandmothers in the Disney Store to try to take a shot at a Massachusetts senator.

The fact this dark mindset extends beyond politicos and the media suggests it is not rooted in any one policy or political tussle, but in something wider and deeper. It's a morbid symptom of a democracy with bigger problems than one administration. It doesn't bode well for the future.

American democracy tells a certain kind of story about itself and its legitimacy: Our government derives its power and authority from the consent of the governed, which means that our government reflects, to some degree, our national character. Even if you look at the government and see nothing at all you approve of, the contractual story goes, you're still following the laws and paying taxes, and that is sufficient proof of assent as far as we're concerned. Thus we all toil under the suspicion that we really do have the government we deserve.

But then there's the clincher that turns a typical democratic concern into our current nightmare. You actually don't have much control over what goes on in government, not because of widespread voter fraud or whatever fantasy, but because a few wealthy donors and their underlings have the privilege of setting the political agenda.

A sense of bitter impotence underlies the political mood on both the left and right, I think, for precisely this reason. When you know that nothing you do matters very much, even victory is frustrating; defeat, meanwhile, feels like utter despair.

Elizabeth Bruenig is an opinion columnist at The Washington Post.