But the imperative to broaden his appeal among Latinos voters has seemed far from his mind. His California events have been disrupted by pro-immigration protesters who he belittles. He recently hurled insults at the California judge overseeing the fraud case involving Trump University, calling him a "Trump hater" and raising questions about his Mexican heritage. Outside his recent San Diego rally, protesters waved Mexican flags and shouted "F--- Trump."
It is yet another reason Republicans are worried about the potential long-term damage that Trump has inflicted on the GOP's image, and their efforts to reach out to younger Latino and minority voters who will be increasingly critical with each election cycle.
The crowds of protesters and clashes outside Trump's rallies in California have served as an eerie reminder of what happened to Republicans here in California after they got behind Proposition 187, the 1994 ballot measure that would have barred immigrants from getting basic state services.
California was still recovering from the depths of recession, and the measure passed overwhelmingly, but ultimately was struck down by the courts.
More lasting was the perception it created among many California voters: that the GOP was anti-Latino. Their embrace of the measure is often cited as one of the central reasons for the steep decline of registered Republicans in California over several decades.
Republican presidential candidates won the Golden State every cycle from 1968 until 1988, during which time California Republicans Richard Nixon and Ronald Reagan were each elected twice to the White House. Bill Clinton broke the GOP's California winning streak in 1992 in his three-way race with George H.W. Bush and Ross Perot. The state has only gotten more blue in the years since.
Trump has said he can win in California even though, in his words, "other GOP candidates wouldn't even come here for a dinner."
But this November many Republican candidates for House, Senate and local races will have to decide whether to stand with Trump on his plans to build a wall and deport 11 million immigrants without papers.
Some see a cautionary tale in the course that California Governor Pete Wilson took in 1994. He was a moderate Republican with mainstream appeal -- but that image changed when he got behind Proposition 187 to save his 1994 re-election campaign.
The strategy worked for him in the short term, but it hurt the image of his party for many years to come. When Wilson was running in the fall of 1994, Republicans made up 37% of registered voters. Today they make up just 27.5% of voters here -- and could soon be overtaken by those who decline to state a party preference.
Trump's approval ratings among Latinos could be key to wins or losses in swing states like Colorado and Nevada. But in a recent Fox Latino poll 74% of Latinos said they viewed Trump unfavorably.
Even with that data, the candidate has given no indication that he intends to strike a more inclusive tone, predicting instead that Latinos will ultimately warm to his candidacy.
"I think the Mexicans are going to end up loving Donald Trump when I give all these jobs," Trump said at his recent rally in San Diego, which drew hundreds of protesters. "I think they are going to love it. I think they are going to love me."