Joe Biden faced a test Thursday that he had avoided so far this year — a solo news conference with questions from the White House press corps.

The news conference was meant to reassure a disheartened group of Democratic lawmakers, allies and persuadable voters in this year’s election that Biden still has the strength and stamina to be president. Biden has tried to defend his feeble and tongue-tied performance in the June 27 debate against Republican Donald Trump as an outlier rather than evidence that at 81 he lacks the vigor and commanding presence that the public expects from the commander in chief.