Republican Jaime Patiño won only 28 percent of the vote when he ran for a Bay Area Assembly seat four years ago. On Tuesday, however, he will be sworn in as a newly elected member of the City Council in Union City.

One big difference: There was no “R” next to his name on last month’s ballot. Voters knew him as a longtime Union City resident, a single dad who knocked on 9,000 doors during the campaign. He didn’t have to tell them he was a Republican when he was running for the nonpartisan council position.

If the “R” label has become toxic for California Republicans after two years of Donald Trump in the White House, for Latino candidates it stands for “radioactive.” When the new class of state legislators was sworn in Monday, there were no Latino Republicans — and 29 Latino Democrats.

“I’m a Republican, always have been a Republican. Been one even longer than Trump,” said Patiño, who said he wrote in a friend’s father’s name for president instead of voting for Trump in 2016. “But we do have a branding issue.”

Patiño knew better than to wave his Republicanism in front of the electorate. In fact, his campaign website featured a photo of him with Democratic Rep. Eric Swalwell of Dublin, who is seriously thinking about running against Trump for president in 2020.

“I stayed away from labels,” said Patiño, 49. “People wanted to talk about national issues, about Trump during the campaign. But I wanted to talk about the two tax measures we had on the ballot. I have an MBA. I work in finance. Who do you want handling the budget?”

California Latinos have been fleeing the Republican label since 1994, when GOP Gov. Pete Wilson won re-election on the strength of his support of Proposition 187. State voters approved the measure, which would have barred undocumented immigrants from public health care and most other government services, but the courts blocked it.

Many middle-aged Latino voters still remember TV ads for Prop. 187, which showed immigrants darting through traffic to cross the U.S. border as the narrator said ominously, “They keep coming.” For years, the ad was played to jeers at Latino get-out-the-vote rallies.

The legacy of Prop. 187: Eighty-six percent of Latinos surveyed in California by Latino Decisions said they voted for a Democratic House candidate last month. Seventy-three percent said Trump had done or said something that made them angry.

“The Trump agenda has created a situation where fewer Latinos can support the party of Trump,” said Assemblywoman Lorena Gonzalez Fletcher, a San Diego Democrat who is vice chair of the California Legislative Latino Caucus.

Some advocates used Trump as a weapon against Republican Latino candidates even in nonpartisan races.

Cecilia Iglesias, running for City Council in Santa Ana, was attacked in mailers as a “Trump extremist” who would “bring hate” to the Orange County city. The evidence: a photo of her with retiring GOP Rep. Ed Royce of Fullerton (Orange County) and House Speaker Paul Ryan, R-Wis., along with a picture of her speaking behind a podium with the Republican Party logo.

“The brand is toxic,” said Ruben Barrales, president of Grow Elect, a group dedicated to developing Latino Republican leaders.

Grow Elect supports candidates for nonpartisan local offices, where they can become known to voters without having to identify as Republican. The effort has been successful to a point — the point where candidates have to enter races where that “R” goes next to their names.

Grow Elect says it has helped 230 Latinos win election to local offices in the last five years. But only one has won a partisan race — Assemblyman Dante Acosta, R-Santa Clarita (Los Angeles County).

And that success was fleeting. After serving just one term, Acosta was defeated last month by Democrat Christy Smith.

“I’ve always said this is a long-term effort,” said Barrales, a former San Mateo County supervisor and adviser to former President George W. Bush. “The Republican Party didn’t get into this situation overnight, and it won’t get out of it overnight.”

Compounding his challenge is that “the Republican Party hasn’t recruited or supported Latino candidates enough,” Barrales said. “They have not made it a priority.”

GOP spokesman Matt Fleming noted that the party put Barrales on its executive committee and its influential initiatives committee, and said Grow Elect’s efforts “are critical to our efforts of inclusion. And we agree that almost every GOP organization can do a better job of recruiting and training candidates that reflect the demographic changes in our state.”

Barrales doesn’t believe the GOP would become more attractive to Latinos if the party suddenly embraced policy changes like a pathway to citizenship for undocumented immigrants or endorsed permanent citizenship for “Dreamers,” the young people who arrived in the U.S. illegally as minors.

“There isn’t a silver bullet that is going to solve this,” Barrales said. “This is about building relationships.”

Kristin Olsen, a former Republican Assembly leader, said the success of Grow Elect candidates for nonpartisan offices shows that “conservative ideals still resonate at the local level. Our ideas aren’t unsound. But the Republican label is so tarnished that they’ve been unsuccessful when they try to move beyond that.

“You have to build trust,” said Olsen, now a Stanislaus County supervisor. “And you can’t build trust if people hate you. People believe that Republicans don’t care about them. If the Republican Party has any future, it has to show that it cares about people. And that will take a monumental effort. That’s not playing with words. That’s about building relationships.”

Building local relationships is how Iglesias won her Santa Ana race, despite the attacks against her. And it is how Republican Lionel Largaespada won a seat on the Benicia City Council. He worked on the city’s Economic Development Board and as a mentor in local schools. He was endorsed by both the Chamber of Commerce and some local labor unions.

Other Latino Republicans can win in California, too, Largaespada said, but they need more support from party leaders. And they need California Republicans to stand up to Trump once in a while, he said.

“The California Republican Party needs to decide sooner or later who they are going to be,” Largaespada said. “Be bold and be practical and be brave. And that entails responding to the president when he is out of bounds.”

Joe Garofoli is The San Francisco Chronicle’s senior political writer. Email: jgarofoli@sfchronicle.com Twitter: @joegarofoli