No! At best majority of Republicans will vote for Trump.
Majority of democrats will obediently vote for Hillary.
Bush versus Hillary = Hillary wins (without Trump in the race, I am betting my farm on Bush nomination)
Bush versus Trump (3rd party) versus Hillary = Hillary wins
Trump versus Hillary = Trump wins.
As if it matters who wins.
Trump third party could surprise. One factor is those Sanders supporters. They could cast their protest vote for Trump if Sanders is treated unfairly. Besides that, a lot of traditional dem votes, including a percentage of blacks, are real unhappy with their current situation, and see the dems doing more for foreigners than for them.
Trump speaks forcefully about getting more American jobs, many Democrats who have been hurt by “fair” trade, illegal immigration and high taxes on businesses will vote for Trump. Trump is a populist kind of guy and many Democrats appreciate that. I bet that there are already many conversations going on in taverns and diners about Trump. He has created excitement like the kind of excitement when the home team wins. It spills over and everyone wants to talk about it. There are many cities and small towns with closed up factories and few jobs. People are hungry for someone who will talk about them and their plight and they have not had someone like that in many years.