> favoritism in a party primary
Do the documents show that or are you inferring it based on what hasn't been leaked?
Even if we grant that the DNC leadership thinks Hillary is the best... so what? It's a political party that takes public input from voters as one factor in deciding a nominee. The DNC shouldn't stuff ballot boxes and should try it's best to make the primaries as fair as possible, but to pretend they don't have like some candidates more than others strikes me as unrealistic.