Sure, but many of them may still reconsider when the actual primary comes around, and they realize deep down that Trump as Republican nominee almost automatically hands the White House to Hillary Clinton. And Trump's disapproval rates are stratospheric - he may have fanatic followers, but most of those who don't follow him now are very unlikely to ever do so. Not like Rubio, Walker, even Bush, who can still convince lots of voters that they're the best candidate.

Maybe. I'm still really not sure to which extent Clinton's issues are genuinely serious. As thoroughly familiar as she is by now to everyone - for better or for worse - it remains puzzling how her approval ratings can swing up and down that much.

You misunderstand - I meant if, and I really doubt this will happen, Trump has already won the Republican nomination. With a choice between Trump and Clinton, there would be millions and millions of voters who might be interested in a centrist third party candidate, be it Bloomberg or perhaps even an actual Republican running as independent, Murkowski style.