After Mamdani Victory, Progressives Call for Primary Challenges to Democratic Establishment
(www.commondreams.org)
You can either get in through primaries and take control from within
You cannot. Both parties are bought and controlled by oligarchs, they will never allow themselves to be voted out.
or you can build a new grass roots party from local elections across the country and build it up over decades

or you can lose.
Yeah that's what all the "reform the party from the inside" folks are doing.