U.S. Senator Bernie Sanders, U.S. Senator Elizabeth Warren, former U.S. Rep. Beto O'Rourke and former Colorado Governor John Hickenlooper (L-R) debate on the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, U.S., July 30, 2019.

Former U.S. Rep. Beto O'Rourke waves as he arrives for the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, U.S., July 30, 2019.

U.S. Senator Bernie Sanders and U.S. Senator Elizabeth Warren shake hands before the start of the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, U.S., July 30, 2019.

Candidate author Marianne Williamson blows a kiss before the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, July 30, 2019.

U.S. Senator Bernie Sanders waits to take the stage on the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, July 30, 2019.

Democratic 2020 U.S. presidential candidates U.S. Senator Elizabeth Warren (L) watches former U.S. Rep. Beto O'Rourke on the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, July 30, 2019.

Democratic 2020 U.S. presidential candidate former Colorado Governor John Hickenlooper speaks on the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, July 30, 2019.

Democratic 2020 U.S. presidential candidates (L-R) U.S., Rep. Tim Ryan, U.S. Senator Amy Klobuchar, South Bend Mayor Pete Buttigieg, U.S. Senator Bernie Sanders, U.S. Senator Elizabeth Warren, former U.S. Rep. Beto O'Rourke, former Colorado Governor John Hickenlooper on the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, July 30, 2019.

U.S. Senator Bernie Sanders and U.S. Senator Elizabeth Warren are seen on television screens in the press file room during the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, U.S., July 30, 2019.

South Bend Mayor Pete Buttigieg (L), U.S. Senator Bernie Sanders and U.S. Senator Elizabeth Warren shake hands before the start of the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, U.S. July 30, 2019.

Democratic 2020 U.S. presidential candidates U.S. Senator Bernie Sanders (L) and U.S. Senator Elizabeth Warren during the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, July 30, 2019.

U.S. Rep. Tim Ryan speaks during the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, U.S., July 30, 2019.

The candidates stand during the national anthem on the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, July 30, 2019.

South Bend Mayor Pete Buttigieg (L) and U.S. Senator Elizabeth Warren (R) watch U.S. Senator Bernie Sanders speak during the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, U.S., July 30, 2019.

Democratic 2020 U.S. presidential candidates Colorado Governor John Hickenlooper, former U.S. Rep. John Delaney and Montana Governor Steve Bullock on the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, July 30, 2019.

Democratic 2020 U.S. presidential candidates South Bend Mayor Pete Buttigieg and U.S. Senator Bernie Sanders on the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, July 30, 2019.

Democratic 2020 U.S. presidential candidate Montana Governor Steve Bullock speaks on the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, July 30, 2019.

Former U.S. Rep. John Delaney speaks on the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, U.S., July 30, 2019.

Democratic 2020 U.S. presidential candidates U.S. Senator Bernie Sanders (L) and U.S. Senator Elizabeth Warren during the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, July 30, 2019.

U.S. Senator Amy Klobuchar speaks during the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, U.S., July 30, 2019.

Democratic 2020 U.S. presidential candidates (L-R) author Marianne Williamson, U.S., Rep. Tim Ryan, U.S. Senator Amy Klobuchar, South Bend Mayor Pete Buttigieg, U.S. Senator Bernie Sanders, U.S. Senator Elizabeth Warren, former U.S. Rep. Beto O'Rourke, former Colorado Governor John Hickenlooper, former U.S. Rep. John Delaney, Montana Governor Steve Bullock pose together on the first night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, July 30, 2019.