Some 600 cities and counties — plus a handful of states — risk about $870 million in federal law enforcement grants as a result of “sanctuary” immigration policies, according to a study by a left-leaning think tank.

The Center for American Progress, founded by former Hillary Clinton campaign Chairman John Podesta, released the report last week. It tracks funding under five major programs.

“It is going to put a lot of pressure in a lot of places on politicians on changing policies, or they risk losing, forfeiting, a lot of money.”

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President Donald Trump has vowed to crack down on sanctuary policies, and issued an executive order early in his tenure instructing the Department of Homeland Security to identify federal funding that could be cut off. That puts him on a collision course with mayors across the country who have pledged to defy the enforcement of federal immigration law.

“It is going to put a lot of pressure in a lot of places on politicians on changing policies, or they risk losing — forfeiting — a lot of money,” said Ira Mehlman, a spokesman for the Federation for American Immigration Reform

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Mehlman said FAIR has not studied the Center for American Progress report in detail. But he said it appears to be a reasonable estimate of what is at stake in the showdown over sanctuary cities. He said local officials might strike a defiant pose now, but he predicted that most will blink if it comes to losing substantial amounts of federal law enforcement funding.

This is especially true, Mehlman said, in cash-strapped jurisdictions. He noted that California Gov. Jerry Brown recently announced that his state is facing a $1.6 billion shortfall.

“Even in a place like California, it’s going to be a hard thing to explain to people,” he said. “I don’t think people are coming to grips with losing the money.”

The report lists five major programs the Trump administration could use to yank funding for jurisdictions that fail to honor requests by Immigration and Customs Enforcement officials to hold illegal immigrants slated for deportation:

The Edward Byrne Memorial Justice Assistance Grant program, which helps states and local government with a range of criminal justice needs.

U.S. Economic Development Administration grants, which help “economically distressed areas” with public works projects and other economic development opportunities.

The State Criminal Alien Assistance Program, which reimburses jurisdictions for the costs associated with detaining immigrants.

The Community Development Block Grant program, which helps states and cities fund housing, infrastructure, and business development projects.

The Office of Community Oriented Policing Services, which provides funding to allow law enforcement agencies to hire additional community policing officers and staff, as well as technical assistance support.

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Eighteen states would be unaffected, since they have no jurisdictions with sanctuary policies. California, meanwhile, would be hit the hardest because the entire state is a sanctuary jurisdiction and is the nation’s most populous state. It risks the loss of $239.5 million, some 27.5 percent of the national total.

New York State ($191.1 million), Illinois ($91.3 million), Pennsylvania ($65.2 million), and Maryland ($35 million) round out the top five.

Jessica Vaughan, director of policy studies at the Center for Immigration Studies, said the estimates appear sound. But she noted that some jurisdictions counted in the report recently have changed their policies to comply with Trump’s executive order. The most notable is Miami-Dade County.

But hundreds of millions of dollars theoretically could be cut off, Vaughan said.

“I don’t expect that to happen because they’re going to give — and I hope they will — give them a chance to adjust their policies,” she said.

Vaughan said it is unclear how aggressive the Trump administration is going to be in fighting sanctuary policies. She said early indications are that officials intend to cast a wider net than an approach pushed last year by Rep. John Culberson (R-Texas), who persuaded then-Attorney General Loretta Lynch to threaten to withhold federal Justice Department grants to the 10 largest sanctuary jurisdictions. Those jurisdictions have until June to change their policies.

Vaughan said the administration currently is revising the form that ICE officials use to request holds on illegal immigrants in local custody.

“That, to me, indicates that this administration is going to approach this differently,” she said.

Some mayors have fought back, vowing to sue if the federal government withholds funds. They argue the federal government does not have the right to use federal funding to compel changes to local policy. They cite the Supreme Court’s Obamacare decision ruling that Congress could not compel states expand their Medicaid programs.

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But Mehlman, the FAIR spokesman, said sanctuary policies are different because they contradict federal law. He noted that Congress has used threats to withhold funding to coerce states into making policy changes ranging from lowering the speed limit to raising the drinking age.

“This is something that’s been used countless times by previous administrations,” he said.