I can’t see it getting to this. Here’s the deal. The pubs and dems can choose who they allow to run under their banner. It’s their club.
However once they allow a candidate to run and the candidate starts to win they can’t change the rules. If trump was so bad they should have never allowed him to run under the party banner in the first place. I say this as a Cruz supporter. If trump wins there is no way in hades these bozo’s will take it away from him. And they know it. Ultimately they will all hail Caesar.
But he doesn’t win until he has 1237 delegates at the convention. If he falls short, the convention will make its decision based on the rules that were in place before any of the candidate names were known. Including the fact that there are rules on how to amend the rules if the convention decides it needs to do so.