 The new survey by the AP NORC Center for Public Affairs Research, conducted two weeks after Biden's debate flop, also found that only about 3 in 10 Democrats are extremely or very confident that Biden has the mental capability to serve as president, down from 40% in an AP NORC poll from February. The findings underscore the challenges the 81-year-old president faces as he works to silence calls from within his own party to leave the race.