Sure, and once again it is up to voters to hold their party accountable. The DNC chair has already resigned. The political fallout depressed turnout and Hillary Clinton ultimately lost. Primary favoritism, whatever form that takes, is not a legal matter, it is a democratic one. At a certain level legal protection doesn't make sense, you said yourself that the closest thing to legality in the DNC, which are party rules, were changed by the party anyway.

Senator Murkowski of Alaska lost her party's primary but ended up winning from write-in votes.

San Francisco's "mainstream media" could fill their front pages with as much praise and justification for the District Attorney as they want, it didn't stop him from being recalled with historic turnout. Getting the media to favor you doesn't mean squat if voters disagree.

The voters are always the biggest factor. Party leaders can pick bad candidates as much as their bosses - the voters - allow them to.