In summary

GOP Assemblyman Brian Maienschein of San Diego is the latest prominent California Republican to switch parties, giving Democrats a majority of epic proportions in the Legislature.

Not that anyone needed more evidence of the Republican Party’s collapse in California. Democrats, in the last election, flipped seven GOP seats in the U.S. House and eight more in the state Legislature. They’ve swept every statewide office since 2010.

But more evidence emerged anyway today, when Republican Assemblyman Brian Maienschein of San Diego announced that he had switched parties and is now a Democrat. A reliably moderate Republican during his six years in the Legislature, Maienschein said his own views had moved to the left as his party veers hard right.  

“Donald Trump has led the Republican party to the extreme on issues that divide our country. But its leadership is not the only reason for changing my party affiliation,” Maienschein said, citing his support for gay rights, abortion access, organized labor, gun control and immigration.

He called President Trump’s conduct “offensive,” “immature” and “counter-productive” and said, “at some point I have to take a stand… and say that this isn’t somebody I can continue seeing as a leader of a party I belong to.”

The assemblyman’s switch is the latest sign that the style of Republican politics emanating from the White House does not play well on the left coast. Last month, California saw another high-profile GOP defection when Tani Cantil-Sakauye, the chief justice of the state Supreme Court, said she had re-registered without party affiliation following the tumultuous confirmation of Justice Brett Kavanaugh, Trump’s pick for the U.S. Supreme Court.

It also bolsters Democratic dominance in the state Capitol to epic proportions, giving them more than 76 percent of the seats in the Assembly. That’s far more than the two-thirds needed to pass tax increases and put constitutional amendments on the ballot, and means Democrats can theoretically pass supermajority bills even if they don’t all agree.

Assembly Republican leader Marie Waldron called Maienschein a “turncoat.”  

“Running away from the fight for a more affordable, efficient and accountable government for hardworking Californians is not the answer,” she said in a statement. “While Brian is enjoying the perks of his new status as a member of the Democrat majority in the Legislature, we Republicans will continue to stand for the people of California.”

The California Republican Party didn’t spend any money to help Maienschein in his re-election campaign last year, which turned out to be extremely close as the Democratic wave washed across previously-GOP regions of the state. Democrats, meanwhile, poured almost $1.2 million into supporting his Democratic challenger, Sunday Gover, who nearly ousted Maienschein.

The assemblyman said the close election did not factor into his decision to switch parties, but it’s hard to imagine he would ignore the signs that constituents in his northern San Diego district are trending blue. Democrat Hillary Clinton won the district in 2016, and Maienschein won re-election as a Republican in 2018 by just 607 votes. By 2020, he would have been on the ballot in a presidential election year, when turnout typically gives Democrats an edge.

“Trump is having a major effect in polarizing the public and… a big effect in turnout in bringing out voters who don’t normally vote in a gubernatorial cycle,” said Mark DiCamillo, a pollster whose research during last year’s election showed that Californians’ overwhelming dislike of Trump helped many Democrats to victory.

“It’s a tough thing for Republicans in California, given the president’s stances,” he said.

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Laurel covers California politics for CalMatters, with a focus on power and personalities in the state Capitol. She's been included in the Washington Post’s list of outstanding state politics reporters...