But what’s to stop the RNC from doing a “Murkowski” and organizing a Write-In campaign for Kasich?
Nothing. It's standard procedure with these has-beens. The shenanigans to win that nomination weren't even subtle. There are still those among the 'pub elite trying to explain to us why what happened with delegates in CO, WY, and LA is okay.
Maybe facts will get them out of their alternate universe. There must be 20 Trump rally locations within an easy one-day drive from Cleveland. They average, what (?) 10,000 people who waited in line hours to attend a Trump rally. That's 2 million Trump supporters. What's to stop a lot of them, over a million, from getting to Cleveland?
It won't just be Trump supporters whose anger would spill over. On the dem side, it is so rigged that Sanders for all practical purposes lost before the first primary vote was cast. There would be across-the-political spectrum anger.