There is no place in the country that will be more affected by the Supreme Court battle over President Obama’s plan to shield millions of undocumented immigrants from deportation than sprawling Los Angeles County.

There are an estimated 1 million undocumented people here, about 400,000 of whom could be eligible for the protected status that Obama says would bring them “out of the shadows.”

County officials plan an aggressive program to sign them up should the justices give the green light. Arguments in the case are scheduled for Monday.

[Supreme Court to review Obama’s immigration policy change]

“I’m looking at the return the county gets,” said Hilda L. Solis, Obama’s former labor secretary who is now chair of the powerful Los Angeles County Board of Supervisors. “Do I want them to pay taxes? Absolutely. Do I want them to be established, with some form of identification? Yes. I think we’re all better off, we’re safer.”

Leo Murrieta and his family were homeless after immigrating to the United States from Mexico, but his parents found jobs working in the Las Vegas casinos. He sees immigration reform as a top issue for this election, but also is optimistic that progress can be made. (Alice Li,Jayne Orenstein/The Washington Post)

It is a familiar view from a Democratic politician in the state with the country’s largest concentration of immigrants.

But the state with the second-largest concentration — Texas — is leading the fight against what it and 25 other states say would saddle them with the cost of providing benefits for millions of people newly eligible for work permits and government programs. The crux of the states’ legal argument is that the program, regardless of its merits, represents an unlawful power grab by the president.

“It is not whether this is the right solution or not,” said Texas Attorney General Ken Paxton (R), whose efforts have led lower courts to block the plan from being implemented. “It’s whether the president is acting outside his constitutional authority.”

[Obama takes immigration leniency plan to the Supreme Court]

It is true that justices will concentrate on whether Obama overstepped his authority and ignored legal procedures in November 2014 when he announced the immigration changes that Congress refused to enact. And the court also will consider whether Texas and the other states have the legal standing to interfere in immigration policy that the White House insists belongs to the executive.

But the societal impact of immigration is debated in the court filings. And there is a stark partisan and ideological divide in the case that Daniel Stein, president of the Federation for American Immigration Reform (FAIR), calls “Donald Trump huge.”

It is impossible to ignore the political backdrop as well.

President Obama's executive order would allow more than 4 million undocumented immigrants to stay in the U.S. for three years, but the Supreme Court could strike it down. (Peter Stevenson/The Washington Post)

The case arrives during a presidential election year in which Trump promises a wall along the border to keep immigrants out and Sen. Ted Cruz (R-Tex.) is adamant that he would immediately reverse Obama’s plans should the court uphold them. On the Democratic side, both candidates have taken positions on immigration to the left of the president.

From California, a broad coalition of educators, religious leaders, business executives, politicians and police has coalesced around a message that it is time for a cease-fire.

“In the last half-century, California has attracted more immigrants — and done more to grapple with immigration policy — than any other state,” said one brief that contends that Obama’s plan would result in “stronger, safer, and more prosperous communities.”

It added, in a mellow tone, “The identity of a thriving city or state depends on the sense of community shared by its inhabitants and those inhabitants in turn draw their dignity and their identities from the social and religious communities they build.”

It is a far different statement from the one California voters made in 1994, when they overwhelmingly passed Proposition 187. It withheld from illegal immigrants public education, all manner of state services and non-emergency health care. The proposal was ruled unconstitutional.

A generation later, the state has gone through “all that bumpy stuff that the rest of the country is experiencing now,” said Manuel Pastor, executive director of the University of Southern California’s Center for the Study of Immigrant Integration.

“We understand that undocumented folks are now part of the state’s fabric,” Pastor said. “One of six people you touch in the labor force is not here legally. I mean, my God, that’s how Southern California functions.”

Obama said it was a recognition of that reality that led him to announce the deportation “guidance” after House Republicans blocked an effort to pass a comprehensive immigration bill.

The plan is called Deferred Action for Parents of Americans and Lawful Permanent Residents (DAPA). It would allow illegal immigrants in those categories to remain in the country and apply for work permits if they have been here for at least five years and have not committed felonies or repeated misdemeanors.

More than 4 million immigrants could qualify for the program and a simultaneously announced expansion of an earlier program, Deferred Action for Childhood Arrivals (DACA), which affects those who were brought to this country as children.

The Obama administration says it is doing nothing more than setting priorities about whom to deport. As a practical matter, it argues, Congress has given the administration only enough money to deport annually no more than about 400,000 of the nation’s estimated 11 million illegal immigrants.

The money should be used to find and deport those with criminal violations, the administration says, rather than immigrants who have established a life here and “anchor families” that would be torn apart by deportation.

But a federal district judge in Texas and then an appeals court ruled 2-to-1 that the plan “is much more than nonenforcement: It would affirmatively confer ‘lawful presence’ and associated benefits on a class of unlawfully present aliens.”

The ruling was welcomed by Texas officials. But it is Obama’s message that resonates in California, where immigrants have become a powerful political force, even if many of them cannot vote. In Los Angeles County, for instance, home to more people than the entire state of Michigan, more than two-thirds of those younger than 18 have at least one parent who is an immigrant.

“There are lots of immigrants who can vote who are sympathetic to the plight of the undocumented,” Pastor said. Moreover, he said, there is a recognition of how integrated the communities have become.

“Forty percent of the people aged 25 to 64 who have a PhD in the state of California are immigrants,” he said. “And those high-skilled immigrants — for instance, in Silicon Valley — are often coupled with unskilled undocumented immigrants, because who takes care of their children? Who prepares their food? Who mows their lawns?”

A USC Dornsife/Los Angeles Times poll published last month showed that nearly two-thirds of Californians think illegal immigration is a major problem in the state; 9 in 10 Republicans think it is either a “crisis” or major problem.

But more than three-fourths of voters said immigrants already here should be allowed to stay, and 60 percent said they should be allowed to apply for citizenship — something DAPA does not contemplate.

Even among Republicans, only 36 percent said immigrants should be required to leave, the poll indicated.

The political impact in a state where Democrats rule has been striking. The place that in the 1990s would have denied state benefits to any illegal immigrant just extended health-care coverage to the undocumented population 19 and younger. This was a compromise from a proposal to extend it to all.

Robin Hvidston, executive director of a group called We the People Rising, said her organization testified against the plan but lacks much support in the California legislature.

“We feel like we don’t have a voice in Sacramento,” she said. “We look with more hope to Congress.”

Solis, whose district of more than 2 million residents is more than 50 percent Latino, said the political climate has changed as the undocumented community has become more established. More than half of those in the county have been there more than 10 years.

“There’s more of a tolerance because there are so many people now who can say, ‘I know somebody who’s in that situation,’ ” she said in an interview in her office. “There are probably some people in this building who are in that situation. I’m pretty sure of it.”

She also credits a younger generation that has taken advantage of DACA and changes that allow them to pay in-state college tuition.

“They paid for their own education because they didn’t qualify for federal or even state aid at the time,” Solis said. “Why would you want to deport those kids? These are going to be the people who replace me or replace you, the bankers, the lawyers.”

She might have been talking about Anabel Cuevas. Her father, Eugenio, came from Mexico in 1989, followed by Anabel and her mother, Victoria, a year later.

Anabel Cuevas grew up in Pasadena and said she did not know she was undocumented until applying for college. She found that she could not accept the scholarship she was offered at a private college because she was not a citizen.

“My parents were always hard workers so we were always, I guess you could say, moving one step up, to a better apartment or whatever,” she said. Her mother has worked as a babysitter and housekeeper; her father is an independent construction contractor, specializing in tile and stone.

When the private college fell through, Anabel Cuevas went to California State University at Northridge. It cost her father about $70,000, he said.

She was able to get a work permit through DACA and now writes computer code for a high-tech company. And hers is one of the many “mixed” families in the county: She has the work permit, her parents are undocumented, and her younger brother, born here, is a citizen.

So the Cuevases would qualify. But nothing is certain. The DAPA program may not survive the court challenge. If it does, it could still be revoked. And the deferral from deportation under DAPA is only temporary.

But she said it is worth speaking out and being identified. She feels there is little danger of being deported in L.A. County.

“But we’re so close as a family, I’ve told [her parents], ‘If you guys get deported, I’m coming with you, and we’ll start a business somewhere else,’ ” she said. “My experience as an immigrant is that nothing is guaranteed.”