THE MISSION for Joe Biden in the presidential debate held in Atlanta on June 27th was clear: to prove his critics wrong, by showing that he was mentally fit and thereby reverse the polling deficit that makes Donald Trump the favourite to win the American election in 2024. Unfortunately, his performance was an unmitigated disaster—perhaps the worst of any presidential candidate in modern history. The president, who is 81 (and would be 86 by the end of a second term in office), stammered indecipherably, struggled to complete his lines of attack and proved his doubters completely correct. Although Mr Trump was in his typical form—meandering, mendacious, vindictive—he somehow appeared the more coherent and lucid of the pair. Mr Biden’s decision to seek re-election rather than standing aside for a younger standard-bearer now looks like a reckless endangerment of the democracy he claims to want to protect.