Democratic presidential hopefuls (from left): Sen. Cory Booker, D-N.J., former Vice President Joe Biden, and Sen. Kamala Harris, D-Calif., onstage before the July debate.

Democratic presidential hopefuls (from left): Sen. Cory Booker, D-N.J., former Vice President Joe Biden, and Sen. Kamala Harris, D-Calif., onstage before the July debate.