WASHINGTON (AP) — As Republicans gather to anoint their presidential ticket in Cleveland, uncompromising opposition to "Obamacare" is getting politically riskier.

Few people were covered under President Barack Obama's health care law when the GOP held its last convention in 2012. Now, Donald Trump's plan to replace the program would make 18 million people uninsured, according to a recent nonpartisan analysis.

Reviled as it may be, Obama's law has changed the nation in ways that many may not want reversed. It means people don't have to worry about being denied coverage due to medical problems, or fear policies that max out while a patient is undergoing chemotherapy. Millions who couldn't afford health insurance now have financial help.

Capturing the White House would finally let Republicans make good on their vow "repeal and replace" the health care law. But ripping apart the social safety net would be politically self-defeating, a new dilemma for the GOP.

"I don't think they can credibly do 'repeal' until they have a solid legislative proposal to replace it," said Lanhee Chen, policy director for the 2012 Mitt Romney presidential campaign. "Politically, you can't really do 'repeal' without the 'replace' coming in right behind it."

Trump "has made some vague pronouncements, but that's not a plan," he added.

Many conservatives are hoping House Speaker Paul Ryan, R-Wis., will have the answer. Ryan has put together a framework for a replacement plan, and he's trying to build GOP consensus. A President Trump would do everything he could administratively to unwind the health care law, while Congress would take on the main work of repealing it and designing an alternative.

"He is going to rely heavily on the Republican House and the Republican Senate to put substantive bills on his desk," said Sen. John Barrasso, R-Wyo., chair of the GOP platform committee.

Even with Ryan's policy expertise, that scenario is also filled with uncertainty.

If Republicans can keep the Senate, they're not expected to have a 60-vote majority that would allow them to ram through legislation. They might have to scale back their health care aspirations from the start.

Possible outcomes could shift from full repeal to rescinding parts of the law that Democrats don't much like either, such as its tax on high-value insurance plans, the employer coverage requirement, and a Medicare cost-control board. Call that "repeal lite."

A GOP replacement — while scrapping Obama's unpopular individual requirement to carry health insurance — would likely have other features similar to the president's approach. Among them are tax credits to help people afford insurance and a provision for people with medical problems to get coverage. Some conservatives would dismiss that as "Obamacare lite."

"Don't get me wrong, there would be a lot of turbulence," said Jim Capretta, a health care policy expert at the business-oriented American Enterprise Institute. "Proposing to move in a different direction will be rocky politically no matter what the circumstances are."

That raises another question: How much political capital would a newly inaugurated President Trump, with far-reaching ambitions on trade and tax policy, want to spend on "repeal and replace"?

All the uncertainty is making people covered under the health care law uneasy. Millions previously uninsured have gotten coverage. The nation's uninsured rate is about 9 percent, a historic low.

Deborah Paddison, a freelance editor and writer from Phoenix, says she would become uninsurable without the Affordable Care Act. As a youngster, she was diagnosed with rheumatoid arthritis, an autoimmune disease that attacks the joints and tissues of the body. She's had more than a dozen surgeries and a kidney transplant. Currently she is getting rehab following an operation to stabilize an artificial hip.

Paddison's monthly premium for a plan through HealthCare.gov is $429, for which she gets a subsidy of $235. Her share comes out to $194.

"There are so many people like me, with a history of chronic disease, who don't yet qualify for Medicare," said Paddison. "We work, we are productive citizens, but basically we would be uninsurable."

The Ryan plan provides a pathway for people who maintain "continuous coverage" to avoid insurance limitations based on their medical histories. But important details remain to be worked out.

While two-thirds of Republicans want the health care law completely repealed, a recent Kaiser Family Foundation poll found that other Americans have different ideas.

About half of Democrats would like Congress to expand what the law does, as Hillary Clinton proposes.

Overall, 33 percent of Americans want the health care law repealed, while 28 percent want to expand it. Others are in the middle.

Those numbers point to enduring divisions, not a clear mandate for repeal.

But don't look for Republicans to back off.

"We are committed to take this on again," said Barrasso. "We have an obligation to the people who voted for us to proceed with 'repeal and replace.'"