Democrats scramble to limit damage as Biden’s stumbling debate heightens age fears

President Joe Biden’s halting debate performance on Thursday night has crystallised concerns about the 81-year-old incumbent’s fitness for office, leading some in his own party to begin questioning whether he should be replaced on the ballot before the November 5 presidential election. But there is no evidence Biden is willing to end his campaign – and it would be nearly impossible for Democrats to replace him unless he chooses to step aside.