WASHINGTON — The $1.9 trillion coronavirus relief package that passed the House on Saturday would make one of the biggest changes to the Affordable Care Act in over a decade, and it could set the stage for a broader overhaul of the health care program — but don’t be surprised if you haven’t heard much about it.

The reforms, which would include temporarily expanding subsidies to purchase insurance and making them available to people of all incomes for the first time, have gotten little attention from either party.

For Democrats, who spent last year debating whether to move to a single-payer system, the more minor changes are uncontroversial and are therefore discussed less than other features of the bill.

Republicans, who have increasingly downplayed their opposition to the ACA, otherwise known as Obamacare, have made little mention of them in messaging against the bill.

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And industry groups, which spent tens of millions of dollars on ads and lobbying campaigns against previous Democratic health care proposals, are largely supportive this time.

“These ACA changes have really flown under the radar and not attracted major opposition from Republicans,” said Larry Levitt, executive vice president for health policy at the Kaiser Family Foundation, a nonprofit health policy research organization.

The biggest ACA-related item in the American Rescue Plan, which the House passed last week, would address one of the most persistent complaints about the law among customers and political opponents alike: sky-high premiums for people who don’t qualify for federal tax credits to help pay them.

The tax credits can go a long way for those who qualify — in many cases, it’s possible to find a plan with zero premiums. But everyone making more than 400 percent of the federal poverty line ($51,520 for an individual) falls off a “subsidy cliff” and has to pay full price. Premiums vary widely depending on local health care costs, and plans often are so expensive that customers forgo insurance.

For the next two years, the American Rescue Plan would expand the tax credits to higher earners and cap the maximum premium anyone is expected to pay at 8.5 percent of their income. It would boost tax credits at lower incomes, as well: People making less than 150 percent of the federal poverty line ($19,320 for an individual) would be expected to pay $0 in premiums for a benchmark plan, for example.

For those with lower incomes, the bill would boost incentives for states to expand Medicaid by having the federal government pick up the tab for new recipients. Twelvestates, including Florida, Georgia and Texas, have refused to accept Medicaid dollars through the ACA. It’s unclear whether the bill would affect their calculations.

The changes, which would be temporary, closely mirror Joe Biden’s health care agenda from the presidential campaign, and Democrats are expected to try to make them permanent down the line.

But they also are low-hanging fruit politically. Unlike with other health care reforms, there are few obvious “losers” beyond fiscal hawks worried about adding to the deficit. The U.S. Chamber of Commerce and top lobbying groups representing insurers, hospitals and doctors have all endorsed the measures, which would pump more money into the system without asking them to cut costs or pay new taxes.

“The industry has been generally supportive of the ACA coverage provisions in the covid relief bill,” Sabrina Corlette, co-director of the Center on Health Insurance Reforms at Georgetown University, said in an email.

Brian Blase, a National Economic Council member in the Trump administration, described the overall Democratic approach as “talk about how evil health insurance companies are but continue to funnel them money.”

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The nonpartisan Congressional Budget Office estimates that the added subsidies would cost $34 billion and that they would insure 1.3 million more people by next year. Blase said that if the subsidies are extended permanently, they could cost the government significantly more by encouraging smaller businesses to offload their workers onto the ACA exchanges.

While some conservative policy thinkers like Blase have criticized the proposal over its cost, congressional Republicans seem less sure how to message against it. House Minority Leader Kevin McCarthy of California never brought it up in his floor speech opposing the relief legislation, focusing instead on other elements of the $1.9 trillion bill.

Many Republicans faced attack ads in 2018 and 2020 for their opposition to the ACA, and the party has largely pivoted to attacking “Medicare for All” instead, even as the Supreme Court considers a Republican-led lawsuit to overturn Obamacare.

But the detente among Democrats, Republicans and big business may not last long.

Democrats are already discussing creating a public insurance option that would compete with private insurers in a future bill. There’s also a push to allow some older Americans to buy into traditional Medicare.

Past public option frameworks have called for reimbursing doctors and hospitals at rates tied to Medicare, which tend to be much lower than what private insurance pays. Proponents argue that that would pressure insurers and providers alike to lower prices. Polls have long found broad bipartisan support for the idea, and Biden has called for both a public option and lowering the Medicare age to 60.

But moving more Americans to government plans is likely to mean less money for doctors, hospitals and specialists. While some proposed versions would adjust rates upward somewhat to ease the transition, a coalition of health care industry groups spent big on ads opposing a public option last year and would be likely to do the same again. Republicans, who have shown little enthusiasm for the idea, would be sure to follow suit.

“The health care industry would fight a public option with everything they have,” Levitt said.