I nstantly last night, the sentence “Joe Biden is unfit for office” was transmuted from a right-wing disinformation campaign to liberal conventional wisdom.

Derek Thompson says the problem was getting a mass of people to “see something at the same time.”

The truth is, it was seen. It was plainly obvious in February, when, after Robert Hur’s report came out saying that Biden was an elderly man struggling with memory problems, Biden then came out in a press conference and gave the kind of performance that causes families to put their aging patriarch into the care of an institution. “My memory is fine!” he shouted, while misidentifying world leaders and forgetting key anecdotes about his life.

And it could be seen for years. Everyone in elite media and Democratic politics knew that Biden was not really up to the job, and sometimes barely competent. They saw his schedule, how light it was — the weeks where there might be two campaign stops in Pennsylvania, followed by several days in one Biden Delaware residence, then several days in another Biden Delaware residence.

But all those anchors, talking heads, and newspaper columnists who spent the whole summer saying Biden was “sharp” as ever were operating underneath the constraints of the echo chamber that was built to tame the narrative about Covid-19. The one that would accuse anyone deviating from liberal moods and taboos as spreading “disinformation.” If you notice too much that Biden doesn’t seen up to the job, you are taking the side of the wicked and the damned.

The echo chamber that sent out the news that Joe Biden is just as capable as he’s always been is the same one that sent out fake stories about Trump Republicans mournfully regretting their decision to go to Covid parties before dying of Covid. Or fake stories about rural hospitals turning away gunshot victims because their emergency rooms were filled with people dying from ingesting too much horse-dewormer because Joe Rogan said it could treat Covid.

None of those stories were immediately subjected to fact-checks and automatic notations from government agencies when they spread on social media. Nor were the sources of those stories — the New York Times and Rolling Stone — given downgrades by professional fact-checkers.

Nope, the lesson internalized by the media is that if you just keep a professional threat of unofficial cancellation hanging over the heads of everyone who works in the opinion-forming institutions, you can keep a party line going long enough to matter.

The whole edifice of techniques, insults, veiled threats, and taboos imposed to keep discipline on Covid messaging was deployed in the service of propping up the sense of Joe Biden’s fitness.

And that whole edifice collapsed last night. Liberal opinion leaders never really convinced the public, but they managed to talk themselves — and those whose moral allegiance leads them to play along — into a shared delusion.

Now watch. If they cannot find the mechanism by which to translate their panic into a successful ejection of Biden from the top of the ticket, the same opinion apparatus will raise up a dense set of interlocking talking points. “Biden had a cold.” “It was just 90 minutes, not reflective of his accomplishments over three-plus years.” “The election is far enough away.” And of course, “Biden may sometimes fail to identify the truth, but Trump is an inveterate liar.”