More Americans may think President Joe Biden tried to sit on a nonexistent chair the other day than know the boring truth that there was, in fact, a chair. The chair-that-was-there was just one of many quick video clips the conservative media ecosystem willed into virality over the past two weeks, leaving fact-checkers and Biden’s team with little chance to catch up. The Republican National Committee, major conservative media outlets and right-wing influencers have succeeded in blasting out videos that they claim show “proof” of Biden’s wandering off, freezing up or even filling his pants with a substance commonly represented...