U.S. House Speaker Paul Ryan (R-WI) delivers remarks before signing a bill repealing Obamacare at the US Capitol in Washington January 7, 2016 Jonathan Ernst/Reuters For years, Republicans in Congress have been clamoring to repeal the Affordable Care Act (ACA), better known as Obamacare, President Barack Obama's signature legislative achievement.

With President-elect Donald Trump set to take office, the GOP may finally get its wish.

According to a new study, however, the repeal would come at a significant price, showing the tightrope the party could be forced to walk on to unravel the law.

The Urban Institute, a left-leaning think tank, analyzed the most likely proposal from Republicans for repeal of the law and found that millions of Americans could lose their insurance if it were to pass.

"We estimate that the partial ACA repeal would increase the number of uninsured people by 29.8 million by 2019, raising the total number of uninsured to 58.7 million people — 21 percent of the non-elderly population — compared with 28.9 million people uninsured if the ACA remains in effect," said the report, which was authored by Linda Blumberg, Matthew Buettgens, and John Holahan.

And the authors said the Republican repeal plan could hit certain groups of working-class families most.

"The vast majority of those becoming uninsured would be members of working families (82 percent), and more than half (56 percent) would be non-Hispanic whites," the study said. "The vast majority of adults becoming uninsured would lack college degrees (80 percent)."

Trump's supporters

Based on exit polling, many of these demographics that would be hit hardest by the repeal voted for Trump in the presidential election. According to exit poll data, non-Hispanic whites favored Trump by 20 percentage points, and non-college educated voters went for Trump by a 5-point margin. Non-college educated whites went for Trump by a 37-point margin.

Urban Institute

Given the wide-ranging plans to repeal and replace Obamacare among Republicans — Trump, House Speaker Paul Ryan, and Secretary of Health and Human Services nominee Tom Price have all suggested or put forward differing plans — the researchers did have to make some assumptions.

They determined that the most likely scenario was a repeal from the budget reconciliation process. Since Republicans do not have a filibuster-proof majority in the Senate, they can likely only repeal those parts of the law that deal with the budget, such as Medicaid expansion and tax credits for exchange-based insurance.

Some GOP lawmakers have suggested they may pass a bill that would repeal Obamacare — but not until 2019. The Urban Institute used that time frame for its research.

The study estimated that spending by the federal government on healthcare would decrease by $109 billion in 2019 and $1.3 trillion form 2019 to 2028.

On the other hand, the medical losses due to uncovered Americans getting care at hospitals would also be significant. Blumberg, Buettgens, and Holahan noted that while uninsured people typically go in for care at a less-frequent rate, they do sometimes end up at the hospital or doctor.

These costs would be spread out between the federal government, local governments, and private healthcare providers. In total, the report estimated total cost for uncompensated care would total $57 billion in 2019 and $656 billion over 10 years.

A bill that passed Congress to repeal Obamacare in 2016 — which was vetoed by Obama — did not have an increase for federal spending on uncompensated care. In that case, more of the burden would fall on local governments and private healthcare providers, according to the Urban Institute.

If Republicans repeal Obamacare immediately, according to the study, the changes would come even more swiftly. an immediate repeal would cause insurers to lose nearly $3 billion for the year as people would likely stop paying premiums as they lose tax credits. Additionally, the number of uninsured would jump by 4.3 million almost overnight.

In order to mitigate these circumstances, Congress would have to take significant steps and pass a replacement bill.

"To replace the ACA after reconciliation with new policies designed to increase insurance coverage, the federal government would have to raise new taxes, substantially cut spending, or increase the deficit," the researchers concluded.