Basically the GOP has their 40% and the Dems have their 40%. The battle is always for the 20% in the middle.
This is why most 3rd party efforts are doomed. 20% of the vote is not going to get it done (which is almost exactly the Perot vote in 1992).
It's too early to say that Trump will have the kind of mass appeal to peel away at those 40% bases. It's possible, considering the political climate out there.
However, I like Trump's chances better as the GOP nominee. He'll get the 40% and most of the 20% in the middle. Maybe even some Democrats. That was the Reagan path to victory in 1980 and 1984.
No. What's happened is the Democrats have gone to the deep, crazy end of their 40% and still have all of them. The GOPe has pandered to this mushy mythical middle to the point that they've angered their base down to 30% or less unenthused, nose-holding votere. All in exchange for negligible gains among the uninterested or ignorant.
Just as 0bama commits his daily abrogation of the Constitution and declares "what are YOU gonna do about it?" the GOPe turns inexorably left and tells their base "where ELSE you gonna go?"
You're gonna find out.