Democratic presidential candidate former vice president Joe Biden, speaks during the Democratic primary debate hosted by NBC News at the Adrienne Arsht Center for the Performing Arts, Thursday, June 27,...

From left, New York City Mayor Bill de Blasio, Rep. Tim Ryan, D-Ohio, former Housing and Urban Development Secretary Julian Castro, Sen. Cory Booker, D-N.J., Sen. Elizabeth Warren, D-Mass., former Texas...

Democratic presidential candidate Sen. Elizabeth Warren, D-Mass., speaks at the Poor People's Moral Action Congress presidential forum in Washington, Monday, June 17, 2019. (AP Photo/Susan Walsh)