FILE PHOTO: Seven of the Democratic US Presidential candidates walk

FILE PHOTO: Seven of the Democratic US Presidential candidates including former U.S. Vice President Joe Biden, Sen. Amy Klobuchar, Sen. Elizabeth Warren and Sen. Bernie Sanders, walk arm-in-arm with local African-American leaders during the Martin Luther King Jr. (MLK) Day Parade in Columbia, South Carolina, U.S. January 20, 2020. REUTERS/Randall Hill/File Photo