This debate was a disastrous opening performance for Biden

The Biden campaign is probably hoping that you did not watch the first presidential debate. Over the course of 90 minutes in Atlanta, the president was only sometimes coherent, delivering meandering statements that were often inaudible, frequently veering off topic, and often running out of his allotted time mid-sentence, so that his message remained unclear or outright incomprehensible to viewers.

It was a disastrous opening performance for a president whose greatest electoral vulnerability is his age and perceptions about his fitness for the demands of his office. Biden’s showing at the first presidential debate has placed his campaign’s least favorite issue – the president’s stamina and acuity – back at the center of the electoral contest.

In one of his more energetic and clear moments, Biden responded to a question about his age by pointing out that Donald Trump is only three years younger than he is, “and a lot less competent”. That may be true, but Trump – the convicted felon who has been found liable for sexual assault, was impeached twice and attempted to overturn the last election when he lost – was forceful, alert and on message, even as he repeatedly lied.

In contrast, when the cameras cut to Biden, he was often slack-jawed, his eyes unfocused, seeming to stare into the middle distance with a look of vacant horror. The contrast was stark. Many of the liberal-leaning voters watching no doubt despaired at Biden’s performance, which they feared would permanently cement the popular opinion that he is simply too old for the job.

He may well be. Even in response to what should have been easy questions, Biden fumbled. He frequently failed to remember words; he often seemed to lose his train of thought, his voice quieting into silence. When asked about abortion rights – the issue that polls show is his most favorable contrast to Trump and his best chance to win in November – Biden described his preferred abortion rights regime as one in which “you go to see a doctor and have him decide if you need help or not” – a scene that relegates women to supplicants, begging for relief from male authorities, rather than citizens endowed with an entitlement to control their bodies and lives in their own right.

Later, when Trump characterized Biden as a criminal, Biden defended his own actions, instead of simply pointing out that it is Donald Trump who is a convicted felon and emphasizing the simple, persuasive core argument for his own re-election: that Trump is a mendacious criminal who will ban abortion and destroy the democratic system of government in pursuit of his own interests.

Instead, Biden attempted to do what the CNN moderators, to their shame, had decided not to do: factcheck Trump’s lies. This meant both that the president was repeatedly sidetracked from talking about his own agenda and also that he was fighting only on Trump’s territory. And he is not equipped to fight well. On social media, some pundits renewed calls for him to drop out of the race so that a younger and more capable candidate could replace him.

There is genuine cause for alarm, because in-between the Democratic panic about Biden’s performance, Trump made the stakes of his re-election clear to everyone. In response to questions about abortion policy, Trump again took credit for the repeal of Roe v Wade, and claimed, falsely, that women in Democrat-controlled states can murder their infants with impunity. His surrogates and allies have put forward multiple proposals to enact a nationwide abortion ban upon his return to office.

In fact, when asked questions about abortion, January 6, climate change, social security, inflation and racial justice, Trump repeatedly declined to answer, instead delivering ominous, hysterical rants about immigrants. He repeated his lie that the 2020 election was stolen. He was asked whether he would accept the results of the 2024 election three times, and three times he refused to answer with a simple “yes” – suggesting that Americans can expect more lies, more attempts to subvert election results and possibly more political violence come November.

If Trump wins this election, the consequences for our country – for our civil liberties, for our economy, for our democratic mode of government, for our international standing, for our aspiration to be a nation of free and equal citizens – will be dire. It is vital to the American project that Democrats beat him. On Thursday night, Biden did not look like someone who can.

• Moira Donegan is a Guardian US columnist