FILE PHOTO: Democratic U.S. presidential candidates Senator Bernie Sanders and

FILE PHOTO: Democratic U.S. presidential candidates former Vice President Joe Biden and Senator Bernie Sanders do an elbow bump in place of a handshake as they greet other before the start of the 11th Democratic candidates debate of the 2020 U.S. presidential campaign, held in CNN’s Washington studios without an audience because of the global coronavirus pandemic, in Washington, U.S. March 15, 2020. REUTERS/Kevin Lamarque/File Photo