The Democratic Presidential Debate at Loyola Marymount University in Los Angeles | Dec. 19, 2019

Former Vice President Joe Biden and entrepreneur Andrew Yang greet well-wishers during a break at Loyola Marymount.  (Kent Nishimura / Los Angeles Times)

The candidates await the start of the Democratic presidential primary debate.   (Brian van der Brug / Los Angeles)

Former Vice President Joe Biden shakes hands with Sen. Bernie Sanders during the debate.   (Brian van der Brug / Los Angeles)

The candidates greet each other before the start of the debate.  (Brian van der Brug / Los Angeles)

Sen. Amy Klobuchar (D-Minn.) waves before the debate begins.   (Brian van der Brug / Los Angeles)

Sen. Elizabeth Warren (D-Mass.) waves ahead of the debate.   (Brian van der Brug / Los Angeles)

Entrepreneur Andrew Yang, left, South Bend, Ind., Mayor Pete Buttigieg, Massachusetts Sen. Elizabeth Warren, former Vice President Joe Biden, Vermont Sen. Bernie Sanders, Minnesota Sen. Amy Klobuchar and businessman Tom Steyer on stage during the sixth Democratic debate at Loyola Marymount University on Thursday in Los Angeles.  (Kent Nishimura / Los Angeles Times)

The candidates on stage at Loyola Marymount.  (Kent Nishimura / Los Angeles Times)

Sen. Bernie Sanders (I-Vt.) and Sen. Amy Klobuchar (D-Minn.) spar during the debate.  (Brian van der Brug / Los Angeles Times)

Sen. Amy Klobuchar (D-Minn.) listens as businessman Tom Steyer speaks during the debate.  (Brian van der Brug / Los Angeles Times)

The candidates on stage during the debate.  (Brian van der Brug / Los Angeles Times)

Entrepreneur Andrew Yang makes a point as South Bend, Ind., Mayor Pete Buttigieg listens during the debate.   (Brian van der Brug / Los Angeles Times)

Sen. Bernie Sanders speaks during the debate.  (Brian van der Brug / Los Angeles Times)

Former Vice President Joe Biden applauds as Sen. Elizabeth Warren (D-Mass.) speaks during the debate.  (Brian van der Brug / Los Angeles Times)

Sen. Elizabeth Warren (D-Mass.) speaks while flanked by South Bend, Ind., Mayor Pete Buttigieg and former Vice President Joe Biden.  (Brian van der Brug / Los Angeles Times)

South Bend, Ind., Mayor Pete Buttigieg speaks while flanked by entrepreneur Andrew Yang and Sen. Elizabeth Warren (D-Mass.).  (Brian van der Brug / Los Angeles Times)

Sen. Bernie Sanders and former Vice President Joe Biden go at each other during a heated exchange at the debate.  (Brian van der Brug / Los Angeles Times)

Former Vice President Joe Biden listens as Democratic presidential candidate Sen. Bernie Sanders speaks during the Democratic debate.   (Brian van der Brug / Los Angeles Times)

Former Vice President Joe Biden makes a point as Sen. Elizabeth Warren listens.  (Brian van der Brug / Los Angeles Times)

South Bend, Ind., Mayor Pete Buttigieg and Sen. Elizabeth Warren (D-Mass.) during an animated moment.  (Brian van der Brug / Los Angeles Times)

Sen. Bernie Sanders speaks as former Vice President Joe Biden listens during the debate.  (Brian van der Brug / Los Angeles Times)

Former Vice President Joe Biden makes a point as Sen. Elizabeth Warren (D-Mass.) listens.  (Brian van der Brug / Los Angeles Times)

Sen. Amy Klobuchar (D-Minn.) speaks while flanked by Sen. Bernie Sanders (I-Vt.) and businessman Tom Steyer.  (Brian van der Brug / Los Angeles Times)

South Bend, Ind., Mayor Pete Buttigieg speaks as Andrew Yang and Sen. Elizabeth Warren (D-Mass.) listen during the debate.  (Brian van der Brug / Los Angeles Times)

Sen. Elizabeth Warren (D-Mass.) speaks as South Bend, Ind., Mayor Pete Buttigieg and former Vice President Joe Biden listen.  (Brian van der Brug / Los Angeles Times)

Sen. Bernie Sanders raises his hand as former Vice President Joe Biden makes a point during the debate.  (Brian van der Brug / Los Angeles Times)