Let me offer what I think is a fair answer. Trump already has most likely 90-95% name recognition. Most of those folks have an opinion of him. For this reason the polls can be considered fairly legit. The results are very very unfavorable. It would take almost a miracle to change the perception of the electorate.
That is a fair answer, which is quite rare these days on FR. It's based of facts and logic, which I like. Changing those voters to a positive opinion of Trump may be difficult. Changing them to a view that "bad as Trump is, Hillary would be worse" is much more achievable. That is a potentially winning campaign strategy.