Threat...

The Democratic Party fears that a potential presidency for Sen. Bernie Sanders (I-Vt.) represents a threat to the party's establishment

Sanders and his allies have repeatedly claimed that the Democratic Party is against his nomination. These fears were exacerbated in November when former President Obama reportedly told advisers in private that he would speak up if necessary to stop Sanders from becoming the Democratic pick. 

On July 28, 2016, Wasserman Schultz resigned from her position after WikiLeaks released a collection of stolen emails indicating that Wasserman Schultz and other members of the DNC staff had exercised bias against Senator Bernie Sanders and in favor of Hillary Clinton in the 2016 Democratic

Sanders has consistently polled near the top of the 2020 presidential primary.