https://en.m.wikipedia.org/wiki/2016_Democratic_National_Committee_email_leak

The leaks resulted in allegations of bias against Bernie Sanders’s presidential campaign, in apparent contradiction with the DNC leadership’s publicly stated neutrality,[8] as several DNC operatives openly derided Sanders’s campaign and discussed ways to advance Hillary Clinton’s nomination. Later reveals included controversial DNC–Clinton agreements dated before the primary, regarding financial arrangements and control over policy and hiring decisions