It was scarcely a year ago that front runner, Jeb Bush and others were floating a narrative that Donald Trump would not be true to the GOP. That Trump would eventually jump ship when he was rejected in the primaries & caucuses; and either run as an independent or support someone other than the GOP nominee.
The scare tactic worked and Donald Trump was forced to sign a loyalty pledge in order to be on the all-important early winner-take-all primary in South Carolina. Now, it's true that Trump initially refused to make the pledge. Trump said he wants to make the deal go both ways. He saw how other candidates like Gary Johnson got shoved off the edge of the stage in 2012, and he wanted to have some leverage to bring that issue before the public.
The RNC would be correct to call upon state GOP officials and politicians and expect them to also bar these unfaithful men from state elective or appointive office. Will Florida Governor, Rick Scott, cooperate? That might not be expected. After all, Gov. Scott was never a party to the contract Jeb, Donald, and other candidates signed.
In 1980, Ronald Reagan expected the same demise and decided to appoint George HW Bush as his designate running mate, to avert the possibility of a replay of 1964.
The well-funded establishment of the GOP are harsh to demand the insurgent candidates pledge loyalty to them, but they have a very poor record of reciprocation.
Jeb Bush and Mitt Romney are openly cheering for Libertarian, Gary Johnson's candidacy. Not because they are fond of the Johnson message; but because they want Trump's failure and their return to the prominent seats of party power.