Former Democratic U.S. presidential candidate Senator Bernie Sanders thursts his fist as he speaks during the first session at the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 25, 2016. REUTERS/Mark Kauzlarich

Former Democratic U.S. presidential candidate Senator Bernie Sanders thursts his fist as he speaks during the first session at the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 25, 2016. REUTERS/Mark Kauzlarich

Former Democratic U.S. presidential candidate Senator Bernie Sanders thursts his fist as he speaks during the first session at the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 25, 2016. REUTERS/Mark Kauzlarich

July 26, 2016 6:58 PM (UTC+8)