I was surprised to find out that, as private organizations, political parties in the U.S. are under no legal obligation to democratically choose their nominees for general elections; parties could choose to select nominees by tennis match.
I was aware that delegates were not legally obligated to vote for the nominee from their district at the political conventions, but typically do so for the first vote.
Nevertheless, in the modern era our major parties have opted for a more-or-less democratic means of choosing presidential nominees, including primaries and caucuses, with the party leadership maintaining some arguable sway in the form of ‘superdelegates’.
The President’s campaign has argued that cancelling the primaries will save money, as he was guaranteed to win in any event, while his primary challengers have derided the moves by the state parties as tyrannical. Which is correct, but apparently is our system. No wonder the corrupt system barely works.