PRESIDENT JOE BIDEN’S performance in his presidential debate against Donald Trump on June 27th called his continued candidacy into question. In the days since, however, the campaign has tried to save Mr Biden, and has succeeded for now. Privately, Mr Biden’s surrogates worked to quell the anxieties of donors worried about throwing good money after bad, and down-ballot candidates worried about their own political survival. Publicly, they came up with a remarkable number of explanations for the president’s display: it was just a cold, a sore throat, a single bad night, a senior moment—well, 90 senior minutes, sure, but don’t you realise that Mr Trump is an existential threat to democracy?