"The Republican Party has been a bad brand name in California politics for a decade, and I think Donald Trump made it a toxic brand," said Thad Kousser, political science chair at the University of California, San Diego. "The clearest flash point for this is in immigration and also the environment."
For one, Republicans lost seven seats in the 2018 congressional midterm elections and the GOP has seen its voter registration decline in historic strongholds of the state, including Orange County — once considered a bastion of conservatism.
Also, some Republican House incumbents and challengers in the recent midterms sought to distance themselves from Trump on immigration and offshore oil drilling, among other issues. But the state GOP is plotting a comeback in 2020, even using the Green New Deal against Democrats.
"California Republicans are conflicted about Trump," said Dan Schnur, a professor of political communications at the University of Southern California and a former longtime GOP strategist who is now an independent. "He still has a very strong and very committed core base of support here. But a lot of elected officeholders are nervous about him because he's so unpopular here."
A poll conducted last month by the Public Policy Institute of California, a nonpartisan think tank, showed only 29 percent of California adults approve of Trump's job performance as president. Yet among California Republicans, the PPIC polling showed Trump enjoys about 75 percent support. That said, just 27 percent of independents and a mere 7 percent of Democrats approve of how the GOP president is handling his job.
"We support the president and are glad he's coming to Los Angeles," said Eric Early, a spokesman for the Los Angeles County Republican Party. "We have lots of policies of the president's that we support."
Still, the anti-Trump vote in 2018 also may have helped Democrats secure a supermajority in both houses of the state Legislature. As of Feb. 10, only 23.5 percent of California registered voters were Republican, down from 26 percent just before Trump was elected president. Those registered as "no party preference" is 28 percent, surpassing the GOP and second to Democrats' 43 percent.
"I don't see a path to the numbers coming back to California until Trump is out of office," said Rob Stutzman, a Republican consultant who served in the administration of former California GOP Gov. Arnold Schwarzenegger.
Stutzman said Trump represents "everything that's opposite" to broaden the party, including being able to reach voters who are younger and more ethnically diverse.
On Friday, Trump is expected to be in the LA area for a fundraiser where dinner is $15,000 per person or $50,000 for the chance to get a picture with the president. There's also $150,000 tickets for those with deep pockets to be part of the roundtable at the private event, NBC Los Angeles reported Tuesday.
Prior to the fundraiser, Trump is scheduled to visit Calexico, a town about 120 miles east of San Diego to see a new 30-foot-tall section of the border wall. The visit comes after Trump threatened on Twitter to shut down the entire U.S.-Mexico border due to alleged immigration "loopholes" he wants Congress to fix.
"Not everybody is happy with everything he does on Twitter, but the actions speak dramatically louder than words," said Shawn Steel, the state's Republican National Committee member.
Immigration is a hot-button issue in California that divides the electorate like few others. With a population of nearly 40 million people, California has more than 10 million foreign-born residents — more than any other state.
"Most Californians believe that immigrants are a benefit to the state," said Mark Baldassare, president and CEO of the PPIC. "Californians have been against building a wall, and in our latest poll most Californians were opposed to the president calling a national emergency in order to build a wall."
Trump has taken a swipe several times as president against California Democratic governors, first Jerry Brown and more recently "grandstanding" Gavin Newsom for asylum shelters and scaling back the state's "so-called Fast Train, which is $Billions over budget & in total disarray." Trump also threatened to cut off funding for wildfire relief in the state.
For his part, Newsom has slammed Trump for "manufacturing a crisis and declaring a made-up 'national emergency'" at the border and admonished the president for threatening to cut off wildfire funding. "Disasters and recovery are no time for politics," he said in a tweet.
The Trump administration is suing California over its so-called sanctuary state laws that are designed to protect undocumented immigrants. The Trump administration and California are fighting over other issues, including health care, fracking, climate change and the census citizenship question.
All told, there are at least 48 lawsuits filed against the administration by the Democratic-led state.
"Regardless of how you feel about the current administration, the reality is that Sacramento must have a cooperative relationship with the federal government," California Assembly Republican Leader Marie Waldron said in a statement to CNBC. "From disaster relief funding to infrastructure projects, we have to work with our federal counterparts and California Democrats' practice of picking fights with the president at every opportunity doesn't help anything."