Bernie Sanders was running as an underdog against Hillary Clinton, who was well financed by the Democratic Party. After Sanders won several primaries, his supporters promised to show up in Philadelphia to demand his nomination as the Democratic Party candidate for president of the United States. Sanders supporters, and Sanders himself, accused the party of running a rigged election campaign that would make Clinton, unpopular among many Americans, the candidate to challenge Donald Trump.
The protests started on the Sunday before the first day of the convention with a march for the environment, which was followed by a four-mile march from downtown Philadelphia to the site of the convention. Many held signs that read “Bernie or Bust” and “Never Hillary.” Leaked documents stolen from DNC computer servers and released on the internet seemed to support the accusations against Clinton.
By Tuesday, Sanders had given up his delegates to Clinton, but protests continued as Clinton became the Democratic nominee for president of the United States.