OPINION: Donald Trump's immigration policy is insane. But at least he has one.

Donald Trump is many things, but a deep thinker with a nuanced grasp of the complexities of public policy is not one of them. Yet he stands firmly at the front of the GOP presidential pack largely because of one issue: immigration. And before you dismiss his thoughts on the subject as the rantings of a simple-minded xenophobe, understand that more than any other candidate, he's offering Republican primary voters some actual concrete ideas for how to address this challenge.