President Biden and his fellow Democrats, for their part, see in the court decision a springboard to build on the 2,000-page statute. They and outside analysts say the law’s survival also provides Democrats a chance to seize on health care in the upcoming congressional elections, portraying the party as protecting Americans’ coverage along with defeating the coronavirus pandemic.

In the hours after the ruling, the Biden administration did not lay out specific elements of the president’s agenda that it will now pursue in Congress. But potential goals include lowering the eligibility age for Medicare and the relatively controversial idea of creating a public alternative to private health plans sold through the ACA insurance marketplaces.

“We’re working on it. Now that we know the Affordable Care Act has passed this last test, we know we’ve got our sea legs under us,” Health and Human Services Secretary Xavier Becerra said in an interview. “Now we have an opportunity to talk about where we can go. Until we had this decision, it would have been folly to talk about those things.”

The battle over the ACA has helped define the polarized political landscape of the past decade. It boosted the tea party in 2010, propelled Donald Trump’s campaign in 2016 and created a dramatic moment when Sen. John McCain (R-Ariz.) blocked his party’s repeal push. More recently, the ACA’s rise in popularity helped Biden’s cause in the 2020 election.

Now Democrats hope to press their advantage. Sen. Patty Murray (D-Wash.), chair of the Senate Health, Education, Labor and Pensions Committee, said the court’s decision “is cause for celebration ・but it must also be a call to further action,” adding that Congress should allow Medicare to negotiate drug prices with pharmaceutical companies, allow more people join Medicare and create a “public option” for health coverage.

Becerra, who as California attorney general led a Democratic coalition fighting to preserve the ACA, noted that Biden’s budget seeks to make permanent a temporary expansion this spring of ACA insurance subsidies, and he said, “We will obviously tackle prescription drug prices.”

Republicans for years ran on a pledge to “repeal and replace” the health-care law, only to fail dramatically when they won control of Washington in 2016. After Thursday’s ruling, they began shifting to an argument that the law needs to be changed but could not realistically be scrapped.

“The ACA is still in place. So I think what we’ve got to do now is think about what we can do in terms of reforms .・・ that will protect people with preexisting conditions, but then also create new choices and options,” said Sen. Josh Hawley (R-Mo.). “Hopefully this will be a spur for some new ideas and new proposals, because pretty much all that’s been on ice since I’ve been here, because everybody said, ‘Well, let’s see what happens with the court decision.’

Asked whether he saw any need for further constitutional questions to be litigated, Hawley, a former Supreme Court clerk, said, “I think this court has made pretty clear that they’re not going to entertain a constitutional challenge to the ACA.”

Sen. Roy Blunt (R-Mo.) added, “The Affordable Care Act gets constantly woven deeper and deeper into the system. It’s eventually going to be pretty hard to unravel from the system. The court had a chance to do that today and didn’t do it.”

Sen. Mitt Romney (R-Utah) said that it was unclear where the politics would head next on health care but that any changes probably would have to come through legislation rather than litigation. “At this stage, it looks like that’s the most immediate course of any change,” he said.

Joseph Antos, a longtime health-care scholar at the conservative American Enterprise Institute, said that Republican rhetoric against the ACA may outlast substantive attempts to dismantle it.

Sen. Ted Cruz (R-Tex.) issued a statement Thursday excoriating Democratic health policies, as well as the court’s reasoning, but he did not propose any specific alternatives. Cruz branded the law a “stepping stone toward a single-payer public option system, which would eliminate private health insurance.”

Antos noted that Republicans, in the minority by narrow margins in both chambers of Congress, are not in a position to pass legislation curtailing the law this year or next. And even if they win control of the House or Senate in the midterm elections, Biden would refuse to sign any such bills for two years after that.

Even so, Antos said, anti-ACA rhetoric could prove useful to the campaigns of House members from pro-Trump districts. “But they should stop talking about it in Washington,” Antos said.

Celinda Lake, a veteran Democratic political strategist, said recent polling and focus groups suggest that health-care could be a substantial midterm issue, with voters eager to improve affordability and keep their medical care stable, especially after the disruptions to people’s lives caused by the coronavirus pandemic.

The court’s basis for upholding the ACA ・that the Republican attorneys general and other plaintiffs who brought the suit lacked legal standing ・“is such a definitive rejection,” Lake said. “I think this will be very energizing for Democrats.”

The Supreme Court has more conservative justices than it did when it ruled in favor of the law in 2012 and 2015, Lake noted, making Thursday’s decision “the last nail in the Republicans’ coffin in terms of getting rid of the ACA.” Two of the three Trump-appointed justices, Amy Coney Barrett and Brett M. Kavanaugh, voted to uphold the law.

Larry Levitt, executive vice president for health policy at the Kaiser Family Foundation, said that while “there will always be legal skirmishes, there are no existential threats [to the ACA] remaining on the horizon.”

As then-President Barack Obama and congressional Democrats sought legislation that would move the country closer to universal coverage, the strategy was to expand private and government insurance alike.

In 2014, the ACA exchanges opened, selling private health plans to people who could not get affordable health benefits through their jobs. That year, some states began to expand Medicaid, the insurance system for low-income residents run jointly by the federal government and states, opening it to people with slightly higher incomes and to adults without dependent children at home.

The number of Americans who have gained insurance under the law has never been as large as originally forecast. But it always has been in the millions, and the Biden administration this year has been pressing to drive the number higher, creating a six-month special enrollment period for the ACA marketplaces that runs through mid-August.

The law, Obama’s signature domestic achievement, was adopted without a single Republican vote in do2010. And in the following few years, it ushered in the most profound changes to health coverage ・and care ・since the creation of Medicaid and Medicare in the mid-1960s.

At the same time, the ACA has remained a source of profound political polarization. Conservatives have depicted it as a tyrannical government takeover of health care, with former Alaska governor Sarah Palin even making false claims that the law would establish “death panels.” Liberals saw it as a long-overdue, if insufficient, effort to expand insurance coverage, control health costs and help protect vulnerable Americans.

Public sentiment has been divided, hovering slightly on either side of 50 percent support, according to years of tracking polls by the Kaiser Family Foundation, a health-policy research group. Support has increased slightly during the past few years, with 54 percent of U.S. adults viewing it favorably this winter, the Kaiser polling shows.

From the time it was enacted, Republicans began trying to dismantle the law through Congress and the courts.

House Republicans tried more than five dozen times to repeal all or part of the ACA. The closest the GOP came was in 2017, when Obama’s presidency ended and Trump moved into the White House after campaigning on a pledge to get rid of the health-care law.

House Republicans passed legislation that year to dismantle major parts of the ACA, but the effort narrowly failed months later in the Senate during a vote that culminated with McCain giving a dramatic thumbs down on the floor of the chamber. Health care also has been an animating issue among Democrats. It was one of the most robustly debated issues during the 2020 presidential primary, with Biden defending the current health-care law and Sen. Bernie Sanders (I-Vt.) and others pressing for a broader system, Medicare-for-all.

Sanders said Thursday that although he was pleased with the Supreme Court’s decision, he would continue working for more extensive reforms.

“The current American health-care system is completely dysfunctional,” Sanders said. “We’ve gained a lot of momentum. Taking on the insurance industry and the drug companies and the whole medical establishment is not easy, but we’re making progress and we are going to win.”

Biden, however, signaled no more receptivity to a single-payer system than he did as a candidate.

“After more than a decade of attacks on the Affordable Care Act through the Congress and the courts,” the president said in a statement, “today’s decision ・the third major challenge to the law that the U.S. Supreme Court has rejected ・[means] it is time [to] move forward and keep building on this landmark law.”

Obama, the president most associated with the law that is often called Obamacare, commented via Twitter. “Today, the Supreme Court upheld the Affordable Care Act. Again,” Obama wrote. “This ruling reaffirms what we have long known to be true: the Affordable Care Act is here to stay.”