If the Party chooses not to reward the top delegate winner then the party will implode. It’s that simple.
Trump could make alliances but why should he? The entire party has conspired against him, including Cruz. Has any other election had a Kasich stay in the race only to pull delegates?
If Cruz wins the most delegates going into the convention I will support him. If not and the nomination is awarded to him, I along with many others will bolt the party for good.
Because he wants/wanted to win the nomination. The rules specified that he needed a majority of the delegates to win, not just a plurality, and it should have been clear to him months ago that wasn't a sure thing.
So, if he really wanted to win the nomination and be something more than just a gadfly, then he have should cared about building the alliances that might be necessary to ensure that he is the nominee. If he chose not to do that, that's on him.
If he wasn't willing to build alliances or work with the party rather than attacking it, then he should have run as an independent. If he made a mistake in choosing not to do that, that's on him as well.
His campaign is where it is because of decisions and choices he made. If it is enough to win him the nomination and election, then all the critics will have been wrong. But if he doesn't succeed, that blame lies squarely on him.
Personally responsibility and all that.
I would offer the VP to Rubio. He bowed out gracefully and helps take Florida and Virginia. Cruz and Kasich I would dump for trying to sabotage me.