The reason that Trump is doing so well with Republican "moderates" is simple

[daleo]

6. I agree - I think his appeal is complicated

Take his position on immigration:

- it appeals to flat-out racists.
- it appeals to nativists, who aren't necessarily racist, but don't want foreigners of any sort.
- it appeals to people who are not necessarily racist, but see immigrants as competitors for jobs.

It's hard to say how the proportions of those three groups break down, but I think it is a mistake to simply dismiss this phenomenon as racism.

His appeal goes to other things as well. Many see him as anti-establishment, a counter to the global capitalism consensus of the establishment elite. To me, he is a sign of that breakdown in support for that consensus. The fact that the Republican establishment is attacking him, just reinforces that belief for his supporters. I can't see him as actually being much of a threat to the establishment, though.