President Biden on Thursday accidentally used Russian President Vladimir Putin’s name when introducing Ukrainian President Volodymyr Zelensky at the NATO Summit, a flub that comes at a vulnerable moment in his campaign. The mistake is likely to turn up the volume on calls for him to drop out of the race after his disastrous debate performance raised questions about his mental acuity. [time-brightcove not-tgx=”true”] “Now I want to hand it over to the President of Ukraine who has as much courage as he has determination.