LOS ANGELES — Democrats are at war with themselves in California, where restless activists are challenging party leaders to resist all things President Donald Trump and move further left on health care, the minimum wage and populist issues.

The conflict could complicate Democratic hopes of winning as many as nine congressional seats in the state, a cluster that would go a long way toward helping the party grab the House majority in next year’s midterm elections.

The Republican civil war has been on full display, with forces aligned with former White House adviser Steve Bannon challenging the GOP establishment and incumbent lawmakers. In California, where Democrats control all levers of power in state government and no Republican has won a statewide election since 2006, the party is feuding over who is doing a better job resisting Trump.

Republicans see a political advantage, arguing Democratic candidates will barrel too far left to win right-leaning seats currently held by the GOP.

“You take what is a very unlikely scenario of victory and make it an impossible scenario of victory,” said former Orange County Republican Chairman Scott Baugh, who is considering a challenge against 15-term GOP Rep. Dana Rohrabacher.

Democrats counter that whatever discord exists is a symptom of unprecedented energy that will help them next year, but acknowledge they’re in new territory.

“I’ve never seen the type of grassroots political activity I’ve seen since the election,” said Mike Levin, one of several Democrats — all of whom back single-payer health care — vying to face vulnerable GOP Rep. Darrell Issa in San Diego’s northern suburbs. “I’ve grown up here and I think we’re just going to have to wait and see. All I can do is talk about our priorities.”

The headline-grabbing challenge to the Democratic establishment from the left is in the Senate race.

State Senate leader Kevin de Leon is running against five-term Sen. Dianne Feinstein, pressing for fiercer resistance to Trump. Backers of Vermont Sen. Bernie Sanders have fumed that the Democratic-controlled state legislature balked at embracing single-payer health care this year, while an activist backed by Sanders’ loyalists almost captured the state Democratic Party’s top job.

Hillary Clinton handily won California’s Democratic primary last year, but even state politicians who embraced her, like de Leon, now sound more like Sanders. For decades, older and more centrist liberals like Feinstein, 84, and Gov. Jerry Brown, 79, have dominated the landscape, creating a backlog of Democrats eager to climb the electoral ladder. Trump’s presidency has shocked the immigrant-friendly, majority-minority state, and liberals have tough demands.

“People are saying, ‘why are you fighting Democrats, you really should be fighting Republicans?’ In California, that’s not the case,” said Eddie Kurtz, president of the liberal group The Courage Campaign.

California’s unusual open primary in which all candidates run on a single ballot has frustrated some liberals because it can favor more centrist candidates like Feinstein. This allows the state’s dwindling number of Republican voters to join moderate Democrats and ensure Feinstein makes the November runoff with whoever challenges her from the left.

In California’s 2016 runoff for Senate, both candidates were Democrats. A similar situation could help California Democrats in 2018 because Republicans may stay home without candidates at the top of the ticket.

But while there may be little danger to Democrats’ Senate prospects in California, some Republicans argue that down-ballot challengers aren’t helping themselves by veering left. Four of the targeted GOP House members’ seats, including Issa’s, stretch into once-famously conservative Orange County, which Clinton became the first Democrat to carry in a presidential race last year.

California’s competitive House districts are clustered in the affluent but rapidly diversifying suburbs between Disneyland and downtown San Diego and in its agriculture-heavy central valley. At the northern end of that valley, in the politically moderate suburbs of Sacramento, one of the state’s few vulnerable Democrats in Congress, Rep. Ami Bera, is being challenged by a 30-year-old lawyer and Sanders supporter, fellow Democrat Brad Westmoreland, as well as a Republican former Marine.

At a forum last month attended by six Democratic challengers in the 10th District to the south — a seat held by Republican Jeff Denham — several candidates repeatedly echoed themes from Sanders’ 2016 outsider campaign.

“If you work for a wage or a salary, you are getting railroaded by the economic system that has taken hold over the last 40 years,” said candidate Mateo Morelos Bedolla, who faulted national Democrats for focusing too much on presidential fundraising while the party “abandoned” working people.

Liberals argue that candidates backing a true progressive agenda will do well, regardless of the district in which they run. Indeed, that argument could be stronger in a state like California.

National Nurses United, one of the strongest backers of Sanders’ presidential candidacy, is already supporting Democratic challengers in three of the targeted congressional districts. Single-payer is “a litmus test” for the union, said its political director, Kenneth Zinn.

“We have a growing mass movement of people who are not content to have elected leaders adopt half-measures that do not accomplish the goal” of providing health care for all, Zinn said.

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The story has been corrected to reflect that Scott Baugh is considering a challenge to Rep. Dana Rohrabacher but has not announced his candidacy.