A poll finds that a growing share of U.S. adults doubt that 81-year-old President Joe Biden has the memory and acuity for the job, turning his coming State of the Union address into something of a real-time audition for a second term. Roughly 6 in 10 say they're not very or not at all confident in Biden's mental capability to serve effectively as president, according to a new survey by The Associated Press-NORC Center for Public Affairs Research.