If you're not voting for Trump now, you're not voting for him. Unless something major happens, I don't see how anyone who isn't convinced by Trump now will be later.
What's the argument?
And yes, you could try "isn't the same true of Hillary?" But the answer is "no." You've either already convinced yourself you're voting for a bigot or you won't. The only question left is if you will vote Hillary or 3rd party (or not at all). And the answer to that question will likely be the result of whether you think Trump may win or not.
That's why we see Hillary's numbers fluctuate greatly and Trump's remain fairly stable.
Nearly every pollster that asks the right questions in swing states and other polls find that the "undecided voter" is predominately pro-Obama. Trump doesn't have more votes to get. He can only win if turnout is down among the Obama coalition.
Win or lose, Trump will receive less votes than Mitt Romney. Mark it down.