“The GOP establishment gets to make the rules!”.........
Before, During or After the convention(s)?
Before.
For Each National Convention,, the Delegates rules committee makes rhe rules.
“Before, During or After the convention(s)?”
Yes.
Same with the Dems, and the Greens, and the Whigs, back when we had Whigs.
It’s their party. You are invited to tell them what you think in the caucuses or primaries, but unless you actively participate and work yourself into a position of influence, you don’t get to state the rules.
Parties are not democracies. They are private entities that select candidates to represent them, and they’re free to do it as they wish.
That’s a concept that many American voters apparently fail to understand.