Not sure what to believe? Bingo. This fever of mistrust is the desired symptom of a powerful virus — a confidence-sapping worm of mutual suspicion — that Russia has planted in the operating system of American democracy. At little cost and with surprising ease, Vladimir Putin and his government have exploited partisanship and social media to serve Russia’s long-term goal of weakening the West by encouraging disorder and disunity. Already, eight months before Election Day, the virus is spreading virtually unchecked, because the very existence of a Russian chaos project has itself become a partisan wedge. Democrats see Putin’s hand in nearly every news cycle, while Republicans increasingly scoff that the whole thing is, to quote the president, a witch hunt.

Millions of us are unsure whether elections will be free and fair, whether the news we consume is real or fake, whether our foreign policy serves national or personal interests. This is a massive victory for America’s enemies. A climate of mutual suspicion at home erodes our ability to affect events abroad. Foreign governments lose confidence in a nation whose leaders — and followers — lack confidence in one another.

Putin has watered this invasive species for much of the past decade. Seizing opportunities on the lawless frontiers of social media, the Russian leader has stoked division, spread disinformation, fanned conspiracy theories and generally mind-gamed the American system.