The silver lining for Democrats is that this gives them a chance to face political reality before they leap off a cliff. The Democratic left must now confront the limits of their power. Mr. Sanders and Elizabeth Warren thought they could bully their agenda through a 50-50 Senate, though they had both lost to Mr. Biden in the 2020 primaries. Their failure to narrow their ambitions doomed the bill.

Yet they somehow persuaded Mr. Biden that he had to govern from the left, in what has proven to be a catastrophic misjudgment. Someday we will learn why Mr. Biden made that decision, though perhaps it is as simple as the fact that throughout his career he has followed his party rather than lead it.

White House chief of staff Ron Klain and domestic policy adviser Susan Rice, the lead architects of this misjudgment, should tender their resignations so Mr. Biden can get advisers willing to govern from the middle. He can start by focusing on the main concerns of voters: coping with Covid-19, reducing inflation, and at least trying to do something to restore order at the border.