The thing about freak accidents is that they do not keep happening. Donald Trump benefited from more than one lightning strike in 2016. His opponent, Hillary Clinton, offered a living, breathing picture of America’s reviled establishment. The director of the FBI, James Comey, was an unusually incompetent investigator. His last-minute intervention helped sway the election. The US electoral college managed to skew a popular defeat for Mr Trump into a victory. Finally, Facebook offered the ideal platform for Vladimir Putin’s fake news blitz.

None of these conditions is likely to recur in 2020 — or at least not in the same way. Yet Mr Trump is betting that history will repeat itself. There was almost nothing, down to the “lock her up” chants against Mrs Clinton, to distinguish Mr Trump’s re-election launch on Tuesday from the themes of his last campaign. Rather than complain about America’s rigged economy, Mr Trump boasts that it has never been stronger. In place of “Make America Great Again”, the new chant is “Keep America Great”. Barring these perfunctory changes, America has seen this Trump movie before.

No one, especially the pollsters, has much of a clue whether his gambit will work. The so-called matchup polls between Mr Trump and putative Democratic nominees are largely academic at this stage. What we do know is that the election will be fought on the most bitter terrain possible. The term “culture war” was coined by Pat Buchanan, the former Nixon speech writer, who led the so-called pitchforks against George H.W. Bush’s establishment Republicans in 1992. The insurgency failed but did enough to wreck Mr Bush’s re-election chances.