Whatever happens in Washington, in the months and years to come, Americans of all stripes who value their self-government must mobilize at every level — not simply once every four years but today and tomorrow and the next day — to win elections and help protect the basic functions of democracy. If people who believe in conspiracy theories can win, so can those who live in the reality-based world.

Above all, we should stop underestimating the threat facing the country. Countless times over the past six years, up to and including the events of Jan. 6, Mr. Trump and his allies openly projected their intent to do something outrageous or illegal or destructive. Every time, the common response was that they weren’t serious or that they would never succeed. How many times will we have to be proved wrong before we take it seriously? The sooner we do, the sooner we might hope to salvage a democracy that is in grave danger.