As the Trump Administration cracks down on undocumented immigrants and threatens to overturn the Affordable Care Act, pushing more than 20 million people off their health care plans, some Seattle leaders are looking for ways to ensure that people living in the city can access health care regardless of their income or immigration status.

To figure out how to accomplish this, they’re looking to the south—specifically, to San Francisco, another high-cost West Coast “sanctuary city” that just happens to have the only truly universal health care coverage system in the country.

The plan, known as Healthy San Francisco, isn’t technically health insurance—only San Francisco residents are covered, and only inside San Francisco’s borders. But it does provide comprehensive health care—everything from annual exams to mental health care to lab tests to addiction treatment—to people making up to 500 percent of the federal poverty line, or about $60,000 for an individual. This group includes independent contractors, lower-middle-class people without employer-provided insurance, and, increasingly, undocumented immigrants, who do not qualify for benefits under the Affordable Care Act.

The idea, according to San Francisco Health Department spokeswoman Rachel Kagan, is to “reduce the dependence of uninsured people on emergency rooms health care,” by getting them “plugged into the health care system earlier, where they can get preventative care.” At its peak, Healthy San Francisco had about 65,000 members; once Obamacare was up and running, enrollment declined to about 14,000.

People who qualify for Medicaid are ineligible for Healthy San Francisco, as are people who already have insurance. (Uninsured people who qualify for the Affordable Care Act can decide to pay the federal penalty and join Healthy San Francisco instead). “It’s supposed to be a program of last resort,” says Alice Kurniadi, a senior program planner at SFDPH, which oversees the program. Healthy San Francisco is funded by the city’s general fund, fees from participants, which max out at $1,800 a year, and a payroll tax on businesses—$2.64 per employee, per hour for businesses with more than 100 employees, and $1.76 an hour for businesses with 20 to 100 workers.

Seattle had a similar tax—derisively referred to as the “head tax” by opponents—for a brief period in the mid-2000s, when the city council passed a $25-per-employee tax to pay for transportation projects. That tax was repealed in 2009, and efforts to reinstate it for other purposes (most recently, to fund the city’s Office of Labor Standards) have failed. (Restaurants challenged the law in San Francisco, but lost; a subsequent court case concluded that the “Healthy San Francisco fees” many had instituted in protested went straight into restaurant owners’ pockets.)

City council Position 8 candidate Teresa Mosqueda, who says she will propose a “Healthy Seattle” plan here if she’s elected in November, acknowledges that there are significant differences between the fiscal and political climates in San Francisco and Seattle that will need to be addressed for the plan to have a shot here.

“The biggest difference is that [San Francisco] already has so much more revenue that they’re able to play with,” including a statewide income tax, Mosqueda says. “Because we have a different revenue system here, we need to have a larger conversation with businesses and employees” about the best way to fund a citywide health-care plan.