“Trump is not popular with the party regulars and I suspect that if he doesn’t win on the first ballot he has no chance at all on the second.”
On that point I agree with you 100%. But Cruz is not exactly Mr. Popularity with the same party bosses (and hacks) that you noted are appointing a lot of the delegates.
The party bosses pretend to hate Cruz. It’s all a scam. We were all sure that McConnell hated Cruz. But his superpac gave Cruz a half million dollars. Graham, another Cruz “hater” did a fundraiser for Cruz.
This “hate Cruz” garbage is just to make people believe Cruz is an outsider.
You're right. It's hard to imagine them trying to insert someone who hasn't run in the primaries, such as Romney or Ryan, though. They could try Rubio, Kasich, or Lil' Jebbie, but they are all proven losers. I think it will be Cruz if Trump doesn't close the deal in the primaries. Trump can still do that and I wouldn't bet against it just yet.