Well put. I don't see dedicated GOP establishment voters staying home, but when it becomes just Trump v Cruz, where do they go? THAT is a big question for late March, and is one of the reasons that the race is closer than it looks. My guess is that they fall to a sitting Senator over a non-politician who could (and hopefully will, if elected) dismantle the entire party organizational leadership. That 18-20 pct makes it a tie game heading to overtime... or a least that is one of the hopes I have to hang my hat on. Trump's mouth, the anti-NE-liberal South, and TX are the others at the moment.
The ONLY reason that a Bush or Rubio voter would vote for Cruz over Trump in a two-way race with no GOPe alternative is to ensure a demorat victory in November, which some of them I believe would clearly prefer.
They know what most of us know: Cruz cannot win in November.
As one FReeper said (and I wish I bookmarked it and I wish I remembered his name):
Cruz has all the electability of Goldwater and all the charm of Nixon.