I believe Reince Priebus made that perfectly clear when he said THE PARTY chooses the nominee, and if you don’t like it, sit down.
Even amateur political students know that the party can do whatever it wants to do, can select whomever they wish...by any criteria they choose in the moment...to be at the head of the ticket.
And, that these primaries and caucii are solely for show.
And that a 3rd party run by Trump will send them all to their grave, especially if he asks his voters to vote AGAINST the Republicans in all down ticket races.
Surely those professionals know that, right?