(Bloomberg Politics) -- A new analysis of a Republican proposal to temporarily continuePPACA premium subsidies if the Supreme Court erases them warns thatit would "only delay" the onset of higher insurance premiums andloss of coverage for potentially millions of Americans.

"Even if a temporary extension of premium subsidies would helpavoid disruption in the short term, it is likely that thedisruption would be only delayed, not avoided altogether. If thesubsidies are ultimately eliminated, potentially millions ofindividuals will drop coverage and premiums will increasesubstantially," the brief by the American Academy of Actuaries said, "unlessother equally strong mechanisms are implemented that wouldencourage participation by a broad cross section of risks."

The analysis evaluates ideas in a bill put forth byWisconsin Sen. Ron Johnson and 31 Republicans thatwould preserve—through August 2017—the Obamacare premium taxcredits that some 7.5 million Americans might lose if the SupremeCourt rules against the government in King v. Burwell nextmonth.

The legislation also repeals the health care law's individualmandate, which the AAA brief said would exacerbate the problems, asit "could result in adverse selection that would raise premiums andthreaten the viability of the market." In plain English, that meanshealthier people would drop their coverage and leave insurancecompanies caring for sicker people, causing them to raisepremiums—what health economists call a "death spiral."

While Johnson's plan has the support of Senator Majority Leader Mitch McConnell,Republican of Kentucky, it isn't faring well with HouseRepublicans. Other Republican contingency options have even lesssupport, leaving open the question of whether the party will unitebehind any solution.

"If the Supreme Court rules, as the law clearly states, thatthose subsidies don't flow through the federal exchange, we'rerecognizing the reality that that's going to be a mess," Johnsontold Bloomberg earlier this month. "We could be looking at a momentof chaos."

The AAA analysis hints at the reason. It warns that swiftelimination of the subsidies would case "massive disruption" in theindividual market, adding that up to "millions of people would dropcoverage, and the average costs of those remaining insured wouldsoar."

At issue in the King case is whether text of the Affordable CareAct prohibits premium tax credits for Americans in some three-dozenstates who buy coverage from the federal marketplace. If the taxcredits are erased, insurance would become unaffordable formillions of Americans.

The case is a double-edged sword for Republicans, many of whomhave asked the Supreme Court to invalidate the subsidies. Such aruling would deal a major blow to President Barack Obama'ssignature legislative achievement, but it would also putRepublicans—both in Congress and on the 2016 presidential stage—onthe hook for offering a plan for the millions of Americans whowould likely lose their coverage or face a spike in premiums.

"I think it's a pretty big concession on our part," Johnson saidof his proposal temporarily continue the subsidies, which someHouse conservatives criticize as a ratification of Obamacare. Thesenator, who will likely face a tough reelection battle in 2016,said failing to respond would "of course" endanger Republicans inthe election, as Democrats would blame them for causing manyAmericans to lose their insurance.

Senator Patty Murray, Democrat of Washington, previewed thepotential attacks from her party. "This analysis," she saidThursday, "shows yet again that when it comes to our health caresystem, Republican policy is to put politics first—ahead offamilies who would lose access to affordable health care coverageand face higher premiums and uncertainty under Republicanproposals."

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