I don't know what proportion of American voters change their vote from one major party to another at an election.
Trump is getting the support of most of the Republican party members but clearly a proportion that are unhappy with the choice. I assume that will be reflected in Republican supporters some of which might well abstain.
I don't read that Clinton, even though not universally popular, seems to generate the same level of disapproval within the Democratic members. So You think he will ? I think a lot depends on the floating voters to make up the difference.
I wonder how many are going to be persuaded by Trump's claims he has the "solutions" to problems that the public presently consider priority, but which seem to be questionable "solutions" wherever they are described.
Getting that sort of trust by simply saying things folk want to hear, and folk not prepared to dig deeper in to analyse, sounds a long shot to me. Preaching to the safe vote who will accept most anything, does not necessarily get mirrored in an increase in the floating vote going your way.