I think Jeb bailing is a godsend for Boobio. Jeb’s votes will go to Boobio and thereby end Cruz’ chances. Carson getting out might have a similar effect, so I hope Carson stays in at least until Super Tuesday.
You’re right about Jeb’s voters. No place for them to go other than Rubio. What will be interesting is to see if, when and how Trump opts to go after Rubio. Trump may have to tread lightly, if he wants those supporters for himself after the dust settles.