During the Presidential debate Donald Trump lost at his own game

The debate was, well, just like Donald Trump: a profoundly depressing demonstration of the coarsening of American politics he has done so much to foster, but terrific entertainment. It was reality TV for the highest imaginable stakes (and in front of a Super Bowl-sized audience) – in which the monarch of reality TV for once came out second best.

In terms of the sheer ferocity of the exchanges, no presidential debate of modern times has offered anything remotely comparable. As always with the bragging and bilious showman, you never knew what would happen next.

The match-up that came closest was in 2000, featuring Al Gore’s visible contempt for, and audible sighing at, his opponent George W Bush, in their first debate. Bush, Gore was contemptuously signalling, was an ignoramus. Back then, though, American politics retained a measure of civility, and conventional rules of debate engagement still applied. And they continued to apply in 2004, 2008 and 2012.

Donald Trump has changed everything – and on Monday at Hofstra University he was at it again: rambling and ranting, interrupting and insulting, wrapping himself in that familiar cocoon of narcissistic infallibility. Only this time, the cocoon didn’t save him. The crowded debate stages of the Republican primaries offered hiding places, and room for the odd breather. This time, one-on-one, there was none.

Sometimes proceedings veered close to chaos, as Trump steamrollered the moderator, NBC’s Lester Holt. But Holt’s loss of control not only raised the entertainment quota of the evening. Far more important, it allowed the candidates to reveal themselves – exactly what debates are supposed to do. Clinton was a touch wonkish, but cool, knowledgeable and unflappable. She also managed to avoid the condescension that proved so disastrous for Gore 16 years earlier.

Trump had the chance to show that the “new’”Trump of recent weeks, the one that acts presidential and has statistically pulled level with Clinton in the polls, was here to stay. But on display was the old Trump: bullying, dyspeptic and hyperbolic. Only for the first 20 minutes or so, when the two argued about trade and the loss of American jobs, did he shine.

Thereafter, goaded by his opponent, the avowed champion of the little guy dug himself into pit after pit, on issues ranging from his business practices – Clinton accused him of “stiffing” many of those little guys who were his contractors – to his mysterious tax returns, and his crude bashing of immigrants and women.

He became steadily ruder and grumpier as the evening wore on, and was reduced afterwards to blaming the “terrible” microphone he was assigned for the debate. “Anybody who complains about the microphone is not having a good night,” Clinton cheerily told campaign reporters on her plane the next morning.

But the reality show may become even more brutal in the days and weeks ahead. Slight Trump and he lashes out, Monday evening confirmed. Now he suggests that nastier stuff is on the way. The presence of the Clintons’ daughter Chelsea in the audience had, he said, persuaded him not to raise the issue of former President Bill Clinton’s extra-marital flings. By in the next debate, in St Louis on 9 October, “I may hit her harder”. We have been warned.