Epic Laugh Test fail: Paul Ryan, Mitch McConnell and the Republican party "elders" are shocked and dismayed that Trump has brought bigotry into their party of "high ideals," and mystified that anyone could associate the "Party of Lincoln" with intolerance. Now let's try the Duck Test. Let's see: It looks like a duck, swims like a duck, and quacks like a duck. It's a duck.
That said, the xenophobia and bigotry are only part of Trump's appeal. He also appeals (rightly or wrongly) to people who are tired of getting shafted by the the economic system and who think it's pathological, for example, to deny that Bush and Cheney lied us into Iraq. You've got to admit that it took real stones for Trump to point that out at the South Carolina debate. That kind of nerve is what many people like in Trump.
In my view, Trump at least has a chance to get things right sometimes, so I see him as less of a threat to our nation than Cruz or Rubio, who are ideologues of the highest order.