The monthslong period in the American electoral system between nomination and election was always its hidden weakness. This year, the trap snapped itself shut upon the national Democrats and former Vice President Joe Biden.

Before the black swan event of the coronavirus arrived, Biden was a plausible if not all that great candidate to run against Trump. An eternity ago, Trump himself was the issue, a man whose persona repelled many millions, and against whom Everyman Biden, while never inspiring, appeared reassuringly sane. Then came the bug, and the crash, and then the great shutdown, and everything changed.