Donald Trump will not likely be able to turn out enough non-Republican voters to win the election. Trump is doing poorly among Republican groups which any GOP candidate must win in order to be successful in a presidential election. It is not very likely that he will be able to attract enough Independents and Democrats because of his controversial statements that have offended so many.
Trump is having problems getting Republicans to vote for him. These are people who are Republicans through and through. They define themselves as a Republican. There is no way that people who have voted Democrat, people who are more liberal-minded, would ever vote for Trump. Even the Republicans don't want him. He said he thinks he'll get some of Bernie Sanders' supporters. There is no way. Those people have views that are as far away from his views as they could possibly get. Trump has a long road ahead and a short time to get there.
The truth is that Trump is not a true political candidate in many respects and he has offended many different parties while bullying people (such as Cruz's wife in vulgar ways that is really unacceptable for a presidential candidate let alone President of the United States). He also has shown that he is clueless about foreign policy and would be likely to start World War III in an attempt for control. He is a greater threat to American safety than even Hillary Clinton and conservative Republicans are starting to see this even though they wish it was not true. He will not win the election.
Republicans don't like Trump, but the people that like Trump are Republican. There aren't enough upset Bernie Sanders voters to swing the election (they couldn't even swing the primary), and even reasonable former republicans and disenchanted democrats are voting for Gary Johnson. Trump doesn't stand a chance unless something super crazy happens before the election.