(CNN) In the epic struggle between President Donald Trump and the Democratic-controlled California state government, a new front is opening that could prove pivotal to the battle for control of the US House of Representatives this fall.

Local officials in Orange County last week threw a twist into the escalating conflict between the nation's capital in Washington and the state's capital in Sacramento by moving to join the Trump administration's lawsuit against the state on the explosive issue of so-called "sanctuary" policies that limit cooperation with federal immigration laws.

The move by the county government to ally with Trump -- which also includes a new policy from Orange County's sheriff intended to undercut the state law -- seems likely to spill into California's critical cluster of congressional races. With Democrats targeting at least seven, and perhaps as many as 10, Republican-held House seats across California, some GOP strategists believe that siding with Trump against the state on the volatile "sanctuary" issue represents the party's best chance to minimize its losses.

"It's a winner for Republicans to fight this battle because as of now the conversation is framed as a public safety issue," says GOP consultant John Thomas, who works with Shawn Nelson, the Republican Orange County Supervisor who led the effort to ally the county with Trump's lawsuit. "In areas like Orange County where registration is starting to tilt against Republicans, those independent swing voters...lean Republican on law and order issues."

An opportunity with peril

And yet the decision by Orange County Republicans to back Trump against the state on immigration represents an enormous gamble for the GOP on two distinct fronts. The intervention risks branding the GOP as anti-immigrant even as the burgeoning populations of Latinos and Asian-Americans are helping to transform Orange County's political complexion from deep Republican red to competitive purple.

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It also bonds local Republicans closer to Trump as the most recent public poll shows that almost two-thirds of all California residents disapprove of his job performance. "Moderate Republican leaning independent voters are going to see that these Republicans...are essentially gluing themselves to Donald Trump's agenda," says Democratic consultant Dave Jacobson, who is working on several races in the area. "And I think it's a toxic brand to associate yourself with."

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In many ways, the Board of Supervisors' choice to support the federal lawsuit seems a throwback to the days when the county was viewed as a hotbed of white backlash conservatism, rather than a reflection of the growing minority presence and shifting partisan allegiances among college-educated whites that allowed Hillary Clinton in 2016 to became the first Democratic presidential candidate to carry Orange County since Franklin Roosevelt in 1936.

It also represents a GOP return to hardline immigration politics a little over two decades after California's Republican Governor Pete Wilson promoted Proposition 187, which sought to deny public services to undocumented immigrants; though the measure passed in 1994 and helped Wilson win reelection that year, it polarized the growing Hispanic population against Republicans and helped tilt California lastingly toward the Democrats.

Democrats need California seats to take House majority

The national stakes in this local maneuvering are so high because Orange County in particular, and California in general, is critical to Democratic hopes of recapturing the House of Representatives in November. In just the Los Angeles media market alone, Republicans are defending five GOP-held seats that Clinton unexpectedly carried against Trump in 2016: the seat held by Steven Knight in the Northern LA exurbs, the Orange County seats held by Dana Rohrabacher and Mimi Walters, and two open seats in the county that are being vacated by Ed Royce and Darrell Issa (which extends into San Diego County). In addition, Democrats are targeting the Central Valley seats held by Republicans Jeff Denham and David Valadao (both of which Clinton carried) and hold more distant hopes of challenging Republican incumbents Duncan D. Hunter (near San Diego), Tom McClintock (near Sacramento) and Devin Nunes (around Fresno) in seats that backed Trump.

Democrats don't have to win all of these seats to recapture the House, but almost any plausible path to a majority requires them to make substantial gains in California. In particular, many Democratic strategists agree with Thomas when he says, "If the House is going to flip it's going to come right through Orange County: those seats are the perfect blend of the kind of seats the Democrats should flip if they are going to win."

Trump's weakness in the state has created the possibility for Democrats to dream of such sweeping gains. In 2016, Clinton beat Trump in California by fully 30 percentage points (61.5 percent to 31.5 percent). That was the widest margin of victory for a candidate from either party in California since Roosevelt in 1936: even native-son Ronald Reagan, in his 49-state 1984 landslide, only won California by a little more than half that much.

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Trump's standing hasn't improved since. The March statewide survey by the Public Policy Institute of California , an independent policy and polling organization, found that just 30% of state residents approved of his performance as president, with 65% disapproving. Even in the Central Valley and Orange County/San Diego, the two areas where most of the targeted GOP House seats are located, the survey found that about three-fifths of residents disapproved of Trump. (Thomas insists his private polling shows Trump in a stronger position in Orange County, though other public surveys have found him facing more disapproval than approval in some of the key districts .)

29 lawsuits and counting

Rather than seek to improve his position in California, Trump has sought to use the state more as a foil to mobilize his base supporters elsewhere (as he did with a new round of Twitter attacks on California Gov. Jerry Brown last weekend). It is difficult to think of another time when a single state and a presidential administration were locked in conflict on as many fronts as Trump and California are today.

Governor Jerry "Moonbeam" Brown pardoned 5 criminal illegal aliens whose crimes include (1) Kidnapping and Robbery (2) Badly beating wife and threatening a crime with intent to terrorize (3) Dealing drugs. Is this really what the great people of California want? @FoxNews — Donald J. Trump (@realDonaldTrump) March 31, 2018

California Attorney General Xavier Becerra has already filed 29 separate lawsuits against the Trump Administration -- and that doesn't even include his defense of the state in the Justice Department's litigation against the California law limiting cooperation with federal immigration enforcement. Becerra's list includes five lawsuits related to immigration, three on health care, three on education and 15 on the environment and climate. Next on the list could be litigation if EPA Administrator Scott Pruitt follows through on the hints that, as part of the administration's efforts to roll back automotive fuel economy regulations, he may seek to revoke the independent authority California has wielded under the Clean Air Act since the 1970s to set independent air pollution and fuel efficiency standards that other states can adopt.

Even this lengthy roster of courtroom disputes doesn't capture the full range of conflicts between Trump and the state. Far more people in California than any other state would have lost health coverage under the repeated GOP efforts to repeal the Affordable Care Act. Likewise, California taxpayers could be adversely affected by Trump's tax law; Californians have received some of the largest benefits from the deductions for state and local taxes and mortgage interest that the recently passed tax bill severely constrained. And the state could be the biggest loser -- both in terms of congressional representation and its share of federal grant programs -- if the administration's decision to add a question about citizenship to the 2020 Census depresses the response rate among immigrants who are not citizens (even if they are here legally).

On other fronts, proposals from Trump and congressional Republicans to cut legal immigration by as much as 40%, to override state firearm concealed carry laws, and to open waters off both coasts to offshore oil drilling would also have a disproportionate effect on California.

A 'lifeline' for California Republicans

Almost all of this is extremely difficult terrain for California Republicans to defend. The effort to repeal the ACA was highly unpopular in the state . The March PPIC poll found that state residents opposed the GOP tax bill by almost exactly 2-to-1. Few Republicans are eager to cheer the prospect of oil derricks sprouting in the view of the seaside mansions of often Republican-leaning voters in Newport and Laguna Beach.

Amid all of these headwinds, Thomas, the GOP consultant, says siding with Trump over immigration enforcement could offer a lifeline to state Republicans. The dispute centers on two recent actions in Orange County to oppose the "sanctuary" legislation the state passed last year requiring local law enforcement to limit its cooperation with federal immigration enforcement.

My Administration stands in solidarity with the brave citizens in Orange County defending their rights against California's illegal and unconstitutional Sanctuary policies. California's Sanctuary laws.... — Donald J. Trump (@realDonaldTrump) March 28, 2018

Trump quickly tweeted his support for the action. Nelson, who is running in the crowded Republican field to succeed the retiring Ed Royce in his northern Orange County district, immediately did a round of appearances on Fox News Channel shows touting the decision. "It's time to end this nonsense and stop being a breakaway republic of the United States of America," Nelson said in one appearance . "We all have to honor the constitution and it's time we get over that even though some in Sacramento don't like the outcome."

Several Republicans running for Congress quickly welcomed the move. Rohrabacher, one of the Democrats' top House targets in the county, even attended the supervisors' meeting to express his support for joining the litigation

The San Diego County Board of Supervisors, also controlled by Republicans, is considering joining the suit as well.

Thomas says challenging sanctuary policies offers Republicans in California, and perhaps beyond, their best chance to close the partisan enthusiasm gap evident in a broad range of elections since 2016. "I think the issue of sanctuary cities is exactly the kind of wedge that Republicans are going to need to bridge that enthusiasm gap," he says.

Other Republicans have been more circumspect. Both Mimi Walters and Steve Knight refused to respond to repeated requests from CNN for comment about the Orange County decision. On the other hand, both voted for legislation that the Republican House passed last summer to punish localities that withhold cooperation from federal immigration enforcement.

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Privately, even some California Democratic strategists acknowledge that defending limits on cooperation with federal immigration enforcement is a tougher fight than almost any of the other Trump initiatives against the state. "If Democrats are campaigning in these much more moderate districts defending sanctuary that's not a winning issue for us," said one Democratic strategist active in the region, who asked not to be identified. "We have a vast gap between the wealthy and working class. We need to be talking about those types of issues. We need to be talking about health care and the environment."

Two pivots for the GOP

Two factors will likely determine whether a focus on sanctuary policies can help California Republicans, especially in Orange County, fortify their defenses against the wave that otherwise seems to be building against them.

One is how Asian-Americans react to the issue. It seems inevitable that this thrust will deepen the GOP's problem among local Latinos. But a key reason the GOP has maintained its grip on the diversifying county for so long is that they run better among the large local populations of Vietnamese, Koreans and Chinese-Americans than they do in most other places. Thomas says private polling shows Asian-Americans take a hard line against undocumented immigration and will welcome the county's resistance to the state law. The supervisors' vote signaled that other office-holders agree: the two Republican Asian-American supervisors on the board who were present supported the motion to join the Justice Department's lawsuit.

But Democrats note that Asian-Americans may view the push against sanctuary cities as part of a broader animus toward immigrants if Democratic candidates can link it to the efforts by Trump and many congressional Republicans to also cut legal immigration. Thomas acknowledges that risk, particularly if the House votes on pending legislation from Judiciary Committee Chairman Bob Goodlatte to significantly reduce legal immigration by slashing the family reunification categories so important in many Asian communities.

The larger gamble for California Republicans is that by allying with Trump in his lawsuit against the state they could strengthen what will likely be a central Democratic argument in the fall elections: the contention that Trump is engaged in a war against California and that local Republicans are, in effect, supporting the enemy against their own constituents.

Bill Carrick, a veteran Los Angeles-based Democratic consultant, says that while Republicans may want to embrace Trump's approach on immigration enforcement without enlisting in the full range of his multiplying disputes with California, "I don't think they get separated out. I think this looks like an assault on California on all fronts." And in that sprawling, searing conflict, California Republicans looking to sharpen the contrast with Democrats on immigration enforcement are accepting the calculated risk of binding themselves more tightly to a president that many in the state consider an invader at the (golden) gates.