As international conspiracies to undermine the world’s last remaining superpower go, the Russian-led plot revealed by a Justice Department indictment on Friday can seem, in its particulars if not its intent, audacious but, as revealed so far, somewhat narrow.

The conspirators stand accused of spreading falsehoods online, hiring Hillary Clinton impersonators at rallies and starting Facebook groups that tried to convince minority voters to stay home or cast their ballots for Jill Stein.

That these efforts might have actually made a difference, or at least were intended to, highlights a force that was already destabilizing American democracy far more than any Russian-made fake news post: partisan polarization.

“Partisanship can even alter memory, implicit evaluation, and even perceptual judgment,” the political scientists Jay J. Van Bavel and Andrea Pereira wrote in a recent paper. “The human attraction to fake and untrustworthy news” — a danger cited by political scientists far more frequently than orchestrated meddling — “poses a serious problem for healthy democratic functioning.”