Matters, almost unbelievably, took a turn for the worse on Thursday when Biden, welcoming Volodymyr Zelensky on stage at the NATO summit, introduced him as “President Putin”. Those in the room heard aides shout “Zelensky” to alert Biden that he’d made the ultimate gaffe.

The audible gasps in the room and the look on Zelensky’s face will surely have given even the most obstinate holdouts in Biden’s inner circle pause for thought on his future as the Democratic Party’s contender in November’s showdown with Trump, three years his junior. Hours later, he referred to Kamala Harris, his vice president, as “ Vice President Trump”.