As was established in 2016, https://observer.com/2017/08/court-admits-dnc-and-debbie-wasserman-schulz-rigged-primaries-against-sanders/

DNC/RNC Primary’s are private affairs that have nothing to do with the right to vote. They only exist to support the “legitimacy” of the parties of Capital. If the parties wanted to, they could unilateral choose their candidates with zero outside/public input. In fact they basically do.