Lots of Trump Supporters Aren't Registered as Republicans

So says NYT:

Donald Trump holds a dominant position in national polls in the Republican race in no small part because he is extremely strong among people on the periphery of the G.O.P. coalition.

He is strongest among Republicans who are less affluent, less educated and less likely to turn out to vote. His very best voters are self-identified Republicans who nonetheless are registered as Democrats. It’s a coalition that’s concentrated in the South, Appalachia and the industrial North, according to data provided to The Upshot by Civis Analytics, a Democratic data firm.

Mr. Trump’s huge advantage among these groups poses a challenge for his campaign, because it may not have the turnout operation necessary to mobilize irregular voters.