Trump has always struck me as an old-school moderate Democrat- liberal on social issues, but strong on law-and-order and patriotism.
The True Story of Donald Trump’s First Campaign Speech—in 1987
Also, this NY Post article from February of this year reports that Doug Schoen, Trump's one-time pollster said:
"When I conducted Trump’s first private presidential poll in 1987, he was planning to run as a moderate independent, not the hard-right Republican he is today. He was once a registered Democrat.”
Donald Trump wanted to be president — in 1988, new book reveals