There are many Republicans who were disappointed that Donald Trump won the Republican nomination for president. They do not like his personality or support many of the things he has said. They reluctantly support him because Hillary Clinton's policies are directly opposed to their own views. They support Trump's policies, but not him.
Initially there were many people claiming they would never vote for Trump. But as the campaigns continued, either the candidate they wanted dropped out, or they realized which candidate was closer to their beliefs, even if neither was an ideal candidate for the voter. Many people dislike Trump, but distrust Hillary knowing the problems she has had in government positions and are afraid of what she would do as President.
Yes, I do believe that many people that previously did not endorse Trump are changing their minds as the election draws near. More and more information is coming out each day about how corrupt Hillary Clinton is and what a bad politician she is. Even if people don't like Trump, they are voting for him because no one wants to see Hillary in office.
I think Trump is going to win in a landslide, not only will his supporters vote for him but anyone who has a minor beef with Clinton is going to vote for him too. The polls don't reflect this because a large section of the population wants to pretend that they are more enlightened and understand the dangers of voting for Trump. They're going to vote for him anyway.