Notice the high level of undecideds. How many Republicans say that they wouldn't vote for Trump right now, but would in November? But, again, we don't have to worry because Trump won't be the nominee (and I fully stand behind my pledge from January in the Forum Community board).
I'd hypothesize that it's lower than the number of Republicans who said they wouldn't vote for Todd Akin but did end up voting for him. I could see a substantial protest vote here going to Gary Johnson especially if Trump keeps shooting himself in the foot (even though he narrowly squeaked by in the GOP primary), to where it could lead to a Hillary victory.