With Joe Biden’s candidacy teetering in the wake of last month’s alarming debate showing, journalists who had covered his presidency full-time for years suddenly asserted that it lacked that most basic political element: credibility.

The trigger was the revelation – disclosed in several news outlets – that a specialist in Parkinson’s disease had visited the White House eight times in as many months. The press secretary, Karine Jean-Pierre, was forced in a live televised briefing on to the defensive over a supposed lack of transparency.

“My first [question] to you is on the credibility of this White House when it comes to talking about the president’s health,” the Associated Press correspondent, Zeke Miller, asked Jean-Pierre, who, taken aback, responded by calling for “a little respect”.

Many journalists increasingly feel they have been bamboozled by a White House culture of denial and non-disclosure. People who pride themselves in holding power to account in the world’s leading democracy have been asking how they could have been so blinded to Biden’s diminishing state before it burst into the open so vividly on the debate stage in Atlanta.