The Soviet Union used to alternate between bald leaders and ones with formidable hair. The US, which is seldom ruled by the smooth of pate, swings around a different axis. It seems to crave a breather after each high-drama president.

The Richard Nixon years gave on to some water-treading under Gerald Ford and Jimmy Carter. Ronald Reagan led to George HW Bush and the prelapsarian tranquillity of the 1990s. After the younger Bush and his still-simmering wars came Barack “No Drama” Obama. It follows that Donald Trump, the author of so much tumult, should prefigure a restful four years under Joe Biden.

Moderate Republicans are counting on it. Not to impugn their principles, but they might be slower to say “Never Trump” if the alternative was as leftwing as Bernie Sanders or his Senate colleague Elizabeth Warren. Mr Biden’s emergence as the Democratic candidate for the White House enabled their apostasy. What threat is there, after all, in a twice-elected vice-president, a voter for welfare reform, a clubbable bipartisan of the old Washington? What radical potential?