He started on the Mexicans.
In fact he told everyone in one of his books that this is exactly what you do.
Trump and the Dark Art of Bad Publicity
“Good news is Melania’s speech got more publicity than any in the history of politics,” he
said, “especially if you believe that all press is good press!”
This was after Melania had plagiarized the shit out of a speech.
"It’s possible to see Trump’s whole campaign as a structure built on colossal missteps, statements that would have torpedoed all other candidacies but have buoyed Trump’s simply by keeping his name in the news. Trump launched his presidential candidacy last summer by descending the escalator at the tower that bears his name and uttering his infamous words about how Mexico is sending to America its criminals and rapists. Those remarks alienated an ally, trashed a major portion of an ethnic group Republicans had vowed to court and set the tenor for a bid that has willfully, almost gleefully defied every poll-tested tenet of modern politics."
This is what Trump set out to do.
"“He is of the mindset that the more his name is dropped, the more a kind of hypnosis, for lack of a better word, there is to the American public,” Jim Dowd, the CEO of Dowd Ink, who did public relations for Trump from 2004 to 2010, told me in a recent interview. “He thinks even a negative piece is a positive for him.”"
And here it is. The quote:
“good publicity is preferable to bad, but from a bottom-line perspective, bad publicity is sometimes better than no publicity at all. Controversy, in short, sells.”
― Donald J. Trump, Trump: The Art of the Deal