The Supreme Court closed an extraordinary three-day review of President Obama’s health-care law Wednesday, with its conservative majority signaling that it may be on the brink of a redefinition of the federal government’s power.

Justices on the right of the deeply divided court appear at least open to declaring the heart of the overhaul unconstitutional, voiding the rest of the 2,700-page law and questioning the underpinnings of Medicaid, a federal-state partnership that has existed for nearly 50 years.

Much can happen between now and the expected ruling this summer, and a far more moderate tone may emerge. Broad statements come more easily in the court’s intense oral arguments than in majority opinions. Between now and the decision, supporters and foes of the law will be able to point to evidence that their side will prevail.

But the rhetoric of the past three days led Solicitor General Donald B. Verrilli Jr. to make an unusual and emotional plea to the justices for restraint. He asked them to respect Congress’s judgment rather than insert themselves into a partisan battle that has roiled the political landscape since the law was passed in 2010.

“The Congress struggled with the issue of how to deal with this profound problem of 40 million people without health care for many years, and it made a judgment,” Verrilli told the justices.

“Maybe they were right, maybe they weren’t, but this is something about which the people of the United States can deliberate and they can vote, and if they think it needs to be changed, they can change it.”

Verrilli made a direct appeal to Justice Anthony M. Kennedy, considered pivotal in the case because he is the conservative most often willing to side with the court’s liberal bloc. On Tuesday, Kennedy said he worried that the law’s mandate that almost every American either secure health insurance or pay a penalty undermines personal liberty and carries a “heavy burden of justification” under the Constitution.

Verrilli spoke about “millions of people with chronic conditions like diabetes and heart disease” who would be “unshackled” from their conditions and about families who would be freed from financial harm caused by high medical costs. The law will help ensure that they “have the opportunity to enjoy the blessings of liberty,” he said.

Paul D. Clement, representing Florida and 25 other states objecting to the health-care law, responded that “it’s a very funny conception of liberty that forces somebody to purchase an insurance policy whether they want it or not.”

The examination of the Patient Protection and Affordable Care Act was unlike any the court has conducted in decades. It has been nearly 50 years since the justices have devoted so much time to a subject.

Before this week’s arguments, many lawyers who practice before the court said privately that they thought the court’s precedents indicated that the Obama administration would emerge the victor. And the court’s four liberal justices showed themselves to be comfortable with the assertion of federal power in the law.

But there was deep skepticism among the conservatives. At times, Verrilli seemed shaken by the intensity of the questions. When Chief Justice John G. Roberts Jr. decided Wednesday that more time was needed to consider the constitutionality of expanding Medicaid, he told Verrilli that he would receive an extra 15 minutes.

“Lucky me,” Verrilli replied, evoking laughter in the crowded courtroom.

Justice Ruth Bader Ginsburg had wondered earlier in the day whether her colleagues were on a “wrecking operation” or a “salvage job” as they were deciding what to do about the rest of the law should the individual mandate be declared unconstitutional.

The court’s divisions were on vivid display Wednesday during a discussion of the law’s Medicaid expansion, which gives states more federal money if they agree to enroll more of the poor. States can refuse, but only if they pull out of the program altogether.

The states challenging the legislation say that is not an option. The Medicaid program has grown so large that it is impossible to forgo federal funding and still provide medical care to the poor, they say.

The question before the Supreme Court is whether the law violates limits the court has set in the past: that the federal government cannot impose conditions “so coercive as to pass the point at which pressure turns into compulsion.”

Liberal justices clearly thought the states’ argument lacked merit.

“Why is a big gift by the federal government a matter of coercion?” asked Justice Elena Kagan, saying the government is giving the states a “boatload of money.”

Justice Stephen G. Breyer said that under Clement’s theory, any expansion of Medicaid that comes with conditions would be unconstitutional. Ginsburg pointed out that “we have never had, in the history of this country or the court, any federal program struck down because it was so good that it becomes coercive to be in it.”

But Justice Samuel A. Alito Jr. said that in passing the health-care legislation, Congress operated on the assumption that the Medicaid program had become so large and essential that no state could turn down the government’s offer. “When that’s the case, how can that not be coercion?” he asked Verilli.

Kennedy added that states had “no real choice.”

Earlier, the court considered whether the entire law should be scrapped should the individual mandate be declared unconstitutional. Even though there are many elements in the legislation that have no connection to the mandate, including funding for ongoing federal programs, Clement said the entire law should fall.

“Let’s just give Congress a clean slate,” he said.

The government argued that only two provisions of the law — a prohibition against insurers discriminating against people with preexisting conditions and a limitation on how insurers set rates — depend on the mandate. The rest of the law should stand, it said.

Again, the justices seemed to split along ideological lines.

It was in a discussion about what Congress would prefer if the mandate fell — all of the law minus the mandate, most of the law or none of the law — that the court began to discuss the political dimensions of its decision and the partisan climate in which it operates.

Clement was greeted with laughter when he said that if the entire law were struck down, it should take Congress only a few days to pass the parts on which members overwhelmingly agreed.

Later in the day, as Clement presented the arguments of the states he represented against the Medicaid provision, Ginsburg reminded him that other states had filed a brief with the court saying they want the federal expansion.

Scalia asked: “Mr. Clement, I didn’t take the time to figure this out, but maybe you did. Is there any chance at all that 26 states opposing it have Republican governors and all of the states supporting it have Democratic governors? Is that possible?”

“There’s a correlation, Justice Scalia,” Clement replied.