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Jim Kenney, mayor of Philadelphia, speaks during the Democratic National Convention (DNC) in Philadelphia, Pennsylvania, U.S., on Monday, July 25, 2016. The Democratic National Committee gloated as Republicans struggled to project unity during the party's national convention, but they are now facing a similar problem after their leader resigned on the eve of their own gathering. Photographer: David Paul Morris/Bloomberg via Getty Images

Jim Kenney, mayor of Philadelphia, speaks during the Democratic National Convention (DNC) in Philadelphia, Pennsylvania, U.S., on Monday, July 25, 2016. The Democratic National Committee gloated as Republicans struggled to project unity during the party's national convention, but they are now facing a similar problem after their leader resigned on the eve of their own gathering. Photographer: David Paul Morris/Bloomberg via Getty Images