FILE PHOTO: Democratic U.S. presidential candidates South Bend Mayor Pete Buttigieg, Senator Elizabeth Warren, former Vice President Joe Biden, Senator Bernie Sanders, Senator Amy Klobuchar and billionaire activist Tom Steyer stand onstage before the start of the sixth Democratic presidential candidates campaign debate at Loyola Marymount University in Los Angeles, California, U.S., December 19, 2019. REUTERS/Mike Blake/File Photo
