It may seem incongruous today that Bernie Sanders voters would vote for Trump but many of them will realize that a vote for the Wicked Witch of the Ozarks is simply a vote for the Establishment. As the general election develops, Trump will be established as the true anti-establishment candidate. Especially as many of the establishment Republicans are still fighting Trump as their nominee. The rejection of Trump by these establishment Republicans is going to win Trump millions of votes he otherwise would not have gotten if he were being supported by the likes of the Bushes, Romney and others of their ilk. By staying away from the convention, they are doing a huge favor for Donald Trump as he will be able to distance himself from them.
The Bushes are loathed by the Democrats and one of my biggest fears is that they will eventually come around and get behind Trump. To them, I say please don't! Please stay away! As Jesse Jackson would say: "Stay Out da Bushes".
Rank and file Republicans WILL come out for Trump as well as the blue collar Reagan Democrats. Trump will also clean up with the Independents. And as noted, If Trump can get 15% or better of the black vote, there is virtually no chance of a Democrat victory this November.
I'm thinking Trump can get 30% of that vote.