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Although his signature law is in jeopardy, President Barack Obama's work reshaping health care in America is certain to endure in the broad public support for many of its underlying principles, along with conflicts over how to secure them.

The belief that people with medical problems should be able to get health insurance is no longer challenged. The issue seems to be how to guarantee that. The idea that government should help those who can't afford their premiums has gained acceptance. The question is how much, and for what kind of coverage.

A sign is held up that reads "ACA Is Here To Stay" front of the US Supreme Court after a 2015 ruling in favor of the Affordable Care Act. Mark Wilson / Getty Images

"The American people have now set new standards for access to health care based on the Affordable Care Act," former Surgeon General Dr. David Satcher says. "I don't believe it will ever be acceptable again to have 50 million people without access to health care."

Obama's influence will continue in other ways, less visible and hardly divisive:

Medicare is shifting to paying for value, not just volume.

The importance of prevention and front-line primary care is more widely recognized.

Doctors and hospitals have computerized their records systems, even if connectivity remains elusive.

The government has opened up mass files of health care billing data, enabling independent analysts to look for patterns of questionable spending.

But conflict is part of Obama's legacy, too. He leaves the country deeply divided about the government's role in health care.

Related: Will Obamacare Repeal Cost Millions of Jobs?

Passed with no Republican votes, the 2010 health care law broke the pattern of major safety net programs like Social Security, Medicare and Medicaid, which had bipartisan backing. Social Security has stood for more than 80 years; Medicare and Medicaid for more than 50.

"If Medicare had been repealed, stories about Lyndon Johnson would have been different," said Robert Blendon, professor of health policy at the Harvard T.H. Chan School of Public Health. "A legacy is whether you did something that was sustained." Johnson was the Democratic president who won approval of Medicare and Medicaid in 1965.

Already, the Republican-led Congress, taking its lead from President-elect Donald Trump, has started the process of repealing and replacing the health law.

"I really do credit Obamacare with saving my life."

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"Approaches that partisan are difficult to sustain as lasting, permanent features of the health care system," said Mark McClellan, Medicare administrator under Republican President George W. Bush.

Obama also failed to deliver on early promises to cut premiums. From 2009-2016, the amount employees pay in premiums for workplace coverage rose by hundreds of dollars, according to the nonpartisan Kaiser Family Foundation. And the average deductible — the annual amount patients pay before insurance kicks in — went from $533 to $1,221, an increase of nearly 130 percent.

Related: Five Things You May Not Know About Obamacare

The achievements and difficulties of the Obama years are reflected in people such as Karen Rezny.

"I really do credit Obamacare with saving my life," said Rezny, a massage therapist from Austin, Texas.

The health care law, or ACA, enabled her to get better treatment for advanced breast cancer. She was uninsured when diagnosed. Before the law, insurers would have rejected her because of her pre-existing medical condition. Even with a subsidized premium, Rezny said she still struggles with cost.

"What I would hope is that we would look back and say (Obama) got the ball rolling, and then we continue," said Rezny. "He took health care off the House and Senate floor — out of theoretical talk by people who are guaranteed lifetime health care — and actually allowed the people to experience it and have it."

When the law passed, 48.6 million people were uninsured, according to the government. Through the first six months of last year, that dropped to 28.4 million. While employer coverage also grew as the economy strengthened, experts credit the ACA for most of the progress. The law provides subsidized private insurance along with a Medicaid expansion for low-income people.

"It would have never been done without the focus and insistence of this president that we go big," said Kathleen Sebelius, Obama's first secretary of Health and Human Services.

Obama set his sights high, but execution was a problem. When HealthCare.gov went live in 2013, the computer system quickly froze. It took a high-tech rescue effort to get things working for consumers.

"Just because you need to do the top floor doesn't mean you level the entire complex."

The law's complexity also tripped people up. It uses the income tax system to subsidize premiums. Some HealthCare.gov customers saw their tax refunds reduced because they underestimated their incomes when applying for subsidies. Fines on those who remained uninsured hit people in their 30s trying to get traction in life. Officials in many states were alarmed by rising Medicaid spending.

When Republicans won control of the House in 2010, Obama was effectively blocked from legislating fixes. The administration used regulations to try smooth out the law's rough edges, while successfully fighting off two Supreme Court cases that would have gutted it.

Related: Obamacare Premiums Are Going Up

In the face of problems, the White House ceaselessly talked up the benefits of the law. Among the controversial claims was that the law deserved much credit for a historic slowdown in national health care spending from 2009-2013.

"Just nonsense," said Rick Foster, formerly Medicare's chief actuary, in charge of long-range estimates. "Far and away the biggest cause of the slowdown was the Great Recession. That is not to say that the Affordable Care Act didn't have some impact, but I think that was small compared to the effect of the recession and the weak recovery."

History shows that America's social programs got built in stages. Automatic cost-of-living increases weren't part of Social Security originally. Medicare didn't get a prescription benefit for nearly 40 years.

Kris Case of Denver hopes that somehow, something like that can happen with Obama's overhaul. She works in customer relations for a technology company and buys coverage through the Colorado insurance marketplace.

"Think of all the work that has gone into this imperfect thing," said Case, "and to just tear it down to make a point, rather than say it's flawed but we can fix it.

"Just because you need to do the top floor doesn't mean you level the entire complex."