Gordon,
I know you started the thread asking a question only about Trump. But I felt that it had strayed off topic, as most discussions on politics tend to, well before I wrote my first post. It had morphed from being about Trump to the entire GOP field, and I wasn't the first to use the term clown car, so I don't think my post was all that 'uncivil'.
I'll give you my opinion about Trump alone, and why he might be doing well in the polls, but your guess is as good as mine. Many candidates find themselves doing well in polls early in the process, before voters become more educated to their positions and start to take into account such things as how an individual may do in the general election. It occurs with both republicans and democrats. I believe that in 2004, Howard Dean was way out on top of the polls for a period of time before sinking faster than the Titanic, all because of a "Yeehaw....". It happens.
My own opinion of Trump is that I don't like him as a political candidate for the Republicans, because he is not a conservative. He was once a registered democrat. He's been for abortion, drug legalization, high taxes, and other liberal causes. He has donated more money to democrats than to republicans, including Harry Reid and Chuck Schumer. No republican would have done that. Anyone can change positions over time, but he can change within months depending upon which way the wind blows. He isn't disciplined, and has a very immature quality to him. To me, he is not a serious candidate for the US presidency, and he himself perhaps even knows that.
As to why he would be doing well in the polls, certainly name recognition and his celebrity help a good bit. And I think the republicans are looking for someone to take on the old republican establishment. I don't agree with 'how' he says it, but he does strike a chord when it comes to illegal immigration with a lot of republicans. I am not hardcore to the right as you might know, but I myself don't understand how our country can absorb hundreds of thousands of people sneaking across the border every year. Because many are low educated and unskilled, it's a huge burden on a welfare system that is already being over whelmed, in my opinion. We are a nation of immigrants, but we have always done so in a legal manner that checked everyone as they entered. When he says that bad people are coming across the border, and days later the news is about a young girl being shot by an illegal, right or wrong, it instantly gave him added credibility to his statements. It isn't racists to say that people had ought to enter legally, and that we should do as much as possible to close off the border before worrying about the ones who have already entered illegally. So I think his, shoot from the hip style, and not worrying about whether or not it hurts him with votes helped his poll numbers. I like that too. I would much rather know how someone actually feels and stands, than to think I'm being fed less than truthful information by someone so they don't lose votes. Think of Obama and gay marriage, where he was for it, then against it, and then for it once again.
As far as his McCain statement goes, I think that was overblown. He speaks off the cuff, and when you do that, things won't always come out as you would have wanted. It sounded to me like a case of bad humor that didn't work out. It happens. But he corrected himself almost immediately and said a few times that McCain was a war hero...... if only because he was caught. Or perhaps it didn't seem so bad to me, because I am not a fan of McCain either.