There have long been concerns about Joe Biden’s mental state, but the latest revelations from the Department of Justice’s special counsel are the most shocking yet.
In his report into the president’s storage of classified documents from the Obama administration, Robert Hur said that Mr Biden had twice failed to recall the dates he served as vice president, and could not remember when his son Beau had died.
His memory is so poor, they claimed, that it is not worth bringing a prosecution against him for mishandling national secrets because a jury would likely take pity on him as a “well-meaning, elderly man with a poor memory”.
After months of White House spin, making excuses for the commander-in-chief’s apparent mental decline, his aides last night claimed that his poor performance in the interviews was explained by his tiredness from dealing with Hamas’s attack on Oct 7.
However, those close to the president will find it far harder to explain this incident away.
For one thing, these revelations about Mr Biden’s memory do not come from partisan commentary, or from an apparent slip-up on camera while on the campaign trail.
They have been released by a neutral official charged with investigating evidence in this case, and refer to a behind-closed-doors interview, that by the president’s own admission, he took extremely seriously.
Secondly, the explanation that Mr Biden was unable to recall basic facts about his own life because he was dealing with a foreign policy crisis suggests that the demands of office are having a significant effect on his mental capacity.
This time, it is not the case – as it is often claimed – that Mr Biden is simply a “gaffe machine” who makes errors when he speaks publicly.
This memory lapse occurred in private, at a time when he was expected to perform his duties at the highest level.
Democrats, and the people around the president, must now decide whether it is wise for the party to adopt Mr Biden as its nominee for November’s election.
Already, the stories about his trips and gaffes are having a major impact on the polls. Just this week, more than three quarters of voters reported in an NBC survey that they had concerns about the president’s ability to do his job.
The questions about Mr Biden’s personal health are also detracting from his main campaign message: that Donald Trump is a force for chaos in US politics and that his reelection would erode American democracy.
The simple question for Democrat strategists is whether Mr Biden’s mental decline is more troubling to swing voters than Mr Trump’s legal difficulties.
Plan B is complex
The evidence suggests that as the campaign continues, it is the president’s age that will affect the results the most.
The mechanism for a so-called “Plan B” is complex. Already, the campaign is too far advanced for a Biden challenger to enter the race and beat him in an open primary.
Dean Phillips, Mr Biden’s only serious opponent, has failed to pick up more than a smattering of votes in the primary race so far.
However, there is a way for Mr Biden to concede defeat at this summer’s Democratic National Convention.
In theory, it is possible for the party to run a full primary contest, only for the winner to step aside. Behind the scenes, there is discussion of Kamala Harris – his unpopular vice president – taking his place and running against Mr Trump in November.
Mr Biden’s mental state is now more than a sideshow to entertain Republicans and keep West Wing spin doctors busy.
It poses a serious threat to his party, and to the United States more generally.
Democrats must now find a way to tackle it – and quickly.