The problem now is if he ran third party, the Establishment would be perfectly happy with Hillary presidency. Especially if the nominee is Cruz.
This is about saving their power in the GOP, they don’t care about the Presidency.It’s about defeating Conservatives
The GOPe at this point are just trying to preserve their place at the table which is jeopardized by a Trump Presidency. All that corruption and greed would be under attack by President Trump.