Democratic presidential hopeful former Vice President Joe Biden listens as Sen. Kamala Harris speaks during the second round of the second Democratic primary debate of the 2020 presidential campaign season.

Democratic presidential hopeful former Vice President Joe Biden (L) listens as US Senator from California Kamala Harris speaks during the second round of the second Democratic primary debate of the 2020 presidential campaign season hosted by CNN at the Fox Theatre in Detroit, Michigan on July 31, 2019. (Photo by Jim WATSON / AFP) (Photo by JIM WATSON/AFP via Getty Images)