So here is your morning after breakdown:
The current delegate count runs as follows: Trump (621), Cruz (396), Rubio (168), and Kasich (138). Or, to put it another way, Trump (621) and NotTrump (702). The line that somebody needs to get across is 1,237. Trump is a mere five delegates across the halfway line — and so this should be considered halftime. A lot can happen in the last two quarters.
If Trump is defeated honestly at the ballot box, then there is a decent chance he won’t go third party.
If Trump is defeated through monkeyshines on the part of the RNC (e.g. rule changes), then he quite possibly would run as a third party candidate. He does have significant ballot access challenges for the general election, and so in order to ignore that obstacle, somebody would have to make him mad enough to be a true spoiler.
Rubio did the right thing by stepping out. Now Kasich needs to do the right thing and follow him. Staying in would be a sheer vanity move that will help no one but Trump. It is now mathematically impossible for him to win it. Both Rubio and Kasich have maximum leverage now. If they wait until the convention to offer their delegates to help stop Trump, they will be offering to solve a problem that everybody knows they created in the first place. But if they coalesce behind Cruz now (which Jeb should also do), then there is a very good prospect that Trump will be defeated in every primary remaining. And if that happens, it will be impossible for him to claim that the RNC did the dirty on him.
If we ratchet back and forth down to the convention, then the party establishment types will be sorely tempted to broker the thing, and offer their idea of a unity candidate. In a year of High Revolt, in a season of Political Turbulence, they will roll out something acceptable to them, someone dressed in pale pastels. And if they do that it will be disaster. By “disaster,” I do not mean losing the general election when it could have been won. That’s not disaster — that’s something the RNC specializes in. That’s not a disaster, that’s their wheelhouse. When I say “disaster,” I am speaking of it from their vantage point, and am referring to the complete implosion of the party.
The one thing that will confirm that all of the above is what needs to happen will be this. If Trump refuses to debate Cruz, one-on-one, then that will indicate where his fears are. With most political observers being manifestly afraid of Trump, it is worth asking, and asking publicly, “What is Trump afraid of?”