Some 60 years have passed since the first televised debate between the two main candidates for the white house. some of the sequels have been quotable, others soporific, but none quite as dismaying as the one held in ohio on tuesday. whether president donald trumps interruptions were impulsive or calculated to throw joe biden, his democratic opponent, off his stride they made for a fragmented and nasty evening that will have illuminated few americans, and perturbed many.

For all the weakness of the moderator, and the ugliness of the crossfire, the debate did at least sharpen the choice at hand.

It is clear that mr trump is running on a back-to-business platform in a still partly closed economy. mr biden tends more to vigilance against the covid-19 pandemic. after a spate of police violence and protests against it, the president stresses law and order. his opponent, with a nod to police reform, adds justice to that pair of abstract nouns.

As for amy coney barrett, mr trumps nominee to the supreme court, the men are at odds over both the candidate and the rightness of her confirmation before the next president is inaugurated. the coming debates should bring out their differences over china and the rest of the world.

By far the bleakest lesson of the night, though, is that fears for the election itself are warranted. mr trump did not just waver and dissemble when asked whether he would accept defeat in november. he also urged his supporters to go to polling stations and watch very carefully because bad things happen. the evidence that voter fraud is rife, and that it disproportionately benefits the democrats, is thin. but by stoking the idea, mr trump readies a pretext to contest any adverse result for him, and encourages his base to take matters into their own hands. dog-whistling is the politico-speak for such language, but it implies subtlety. mr trump was blatant.

And this is to say nothing of his eerily ambiguous message to white nationalists. somebodys got to do something about antifa and the left, his formulation on the night, could be a general observation or something much darker. either way, the president had the opportunity to be plain in his condemnation of the far-right, and did not take it. snap polls suggest that mr biden, though often frail-seeming and quick-tempered, won the debate. but no one with a care for american democracy can have switched off feeling anything but queasy.

Commentators often wonder at mr trumps indifference to voters who are not already with him. he certainly made no appeal to them. the infrastructure-building protector of public services of 2016 has become much narrower in his vision. tonally, too, his rudeness was hardly tailored to undecided voters in the suburbs. it is odd behaviour for a man trailing in the polls.

But this line of criticism has always assumed that victory in the conventional sense is mr trumps aim. this seems increasingly naive. it is possible that the president views a tainted election, perhaps resolved by the courts, as his best chance of remaining in power. at the least, if he can persuade a large minority of americans that he was cheated, it would open the way for him or a relative to run as an aggrieved party in 2024.

Hence in a year of lethal contagion, of state violence and economic carnage, none of these troubles is quite the largest issue at stake in november. that is americas democratic process itself. the worst presidential debate in memory was also the most ominous. no one will have savoured it more than the nations autocratic enemies.