Trump seems immune to his own mistakes, or, what we observers would call mistakes. He calls Mexicans rapists, and his popularity does not go down. He insults John McCain, and, by proxy, most veterans, and still his popularity remains the same. Trump answers a question about misogyny by proving that he is a misogynist, and so far, no harm done to his candidacy. What is going on?
I am no expert on American politics, but I do know something about the use of xenophobia and other forms of hate for political gain. I think the key here is that Trump is appealing to white males (mostly) who are angry about their place in society. Well, angry about the possibility that their privileges are no longer unquestioned, that their supremacy is no longer accepted quite so much. This anger seems alot like the tea party anger--not really policy specific but other-targeted. Remember, Trump was quite a loud birther, so he is not changed his spots.
And he is getting the attention because he is doing stuff to get attention. He stands out from a field of 17 because he is utterly without shame, making Mike Huckabee seem almost modest by comparison. And with a field of 17, a guy with 24% support is king. I have not examined the polls carefully, but I doubt that Trump will actually gain heaps of support as the field is winnowed. Not just because Fox and the GOP establishment will rally around alternatives, but because there is, luckily (and maybe this is wishful thinking on my part), a limit of how many truly crazy/hateful/whatever folks there are in the GOP. No self-respecting evangelical Christian could vote for him, not just because he is not anti-choice but because of everything he stands for: divorce, greed, gambling, etc. And those folks make up a big hunk of primary voters.
Anyhow, Trump is demagoguing his way along for the time being. I would bet against him, shorting him on the prediction markets. But I would not bet against him sticking around for a while longer--we love a good train wreck and we love a good circus. Right now, we are getting both.