Erin Meredith, 37, divorced and single mother of two children, is an office manager in Bastrop, Texas. A self-described “staunch Republican,” Meredith has enrolled in Obamacare and receives a subsidy to help pay her monthly premium. (Ilana Panich-Linsman/For The Washington Post)

Approximately 6.4 million Americans could lose their subsidies for health insurance if the Supreme Court rules against the Obama administration this month, according to new federal data released Tuesday.

Enrollment data for the health-care law shows that 10.2 million people had signed up and paid their premiums as of March, according to the Centers for Medicare and Medicaid Services. Of those, 6.4 million are receiving subsidies to help them pay for private insurance in the 34 states that are relying on the federal health insurance marketplace, HealthCare.gov.

If the court sides with the challengers, those consumers would lose their subsidies, or about $1.7 billion a month, according to the data.

Although health researchers made similar projections earlier this year, the government figures released Tuesday provide the best available estimate of how many people would be at risk, said Larry Levitt, a senior vice president at the Kaiser Family Foundation.

“These are the people we now know are receiving subsidies that would be lost if the court sides with the challengers,” he said. “The amounts are substantial.”

The Affordable Care Act is facing another challenge at the Supreme Court in King v. Burwell, which deals with subsidies for health insurance. The case could cut out a major provision of Obamacare, causing the law to unravel. Here’s what you need to know about the case. (Julie Percha/The Washington Post)

The plaintiffs in King v. Burwell argue that people who buy coverage on the federal exchange are not entitled to subsidies. (Consumers in the 16 states and the District of Columbia that set up their own insurance exchanges would not be affected.) The Obama administration argues that Congress intended to help everyone who qualifies for it. The court is expected to issue its ruling by the end of the month.

The subsidies are scaled to income. The average subsidy is $272 per month.

Many who receive subsidies through the federal marketplace are white and live in the South, according to a recent Urban Institute analysis. Half have full-time jobs. Many live in states such as Florida, Georgia, Louisiana, North Carolina and Texas — states led by Republican officials who oppose the health-care law and have balked at setting up their own exchanges. Another big group lives in the Midwest, in states such as Illinois, Indiana, Ohio and Wisconsin.

Florida would be most affected in terms of the number of people losing subsidies (1.3 million) and the total monthly value of those subsidies ($389 million), with Texas ranked second in both categories (832,000 residents losing a total of $206 million per month), according to a Kaiser Family Foundation analysis of the new federal data.

Subsidized enrollees would face an average effective premium increase of 287 percent if they had to pay the full cost of coverage, Kaiser researchers found.

Those in Mississippi would fare the worst; the average enrollee faces an average premium increase of 650 percent if the court rules for the challengers. Counterparts in Alaska and Utah could face premium hikes of more than 500 percent. Researchers calculated increases using average premiums by state as reported previously by the Health and Human Services Department.

The states with the highest proportion of consumers receiving subsidies are: Mississippi (94.5 percent), Florida (93.5), North Carolina (93.2), Wyoming (92.9) Louisiana (92), Arkansas (91.1), Georgia (91.1), Alabama (90.7), Wisconsin (90.7), Alaska (90.5) and South Carolina (90.2).

With the exception of Arkansas, these are also some of the states that have not expanded their Medicaid programs to cover more low-income adults. As a result, the stakes in the Supreme Court case are higher in these non-expansion states, Levitt said. States that expanded Medicaid were able to give health coverage to many more low-
income adults.

Florida Gov. Rick Scott (R) said Tuesday that he won’t propose a new plan if the Supreme Court rules against the health law and revokes coverage for Floridians.

“I think it has to be a federal fix,” he told reporters at an economic summit he hosted in Orlando on Tuesday for seven GOP presidential candidates.

One of the contenders in attendance, Wisconsin Gov. Scot Walker said, “We will ultimately push back” if he faces pressure to come up with a solution to gaps in coverage.

“This is a problem created by this president and the previous Congress,” he said. “It’s something that requires a solution at the federal level. States didn’t create this problem, the federal government did. And they should fix it.”

The overall enrollment numbers show that almost nine out of 10 consumers who signed up for coverage through the exchanges paid their premiums as of March 31, when open enrollment ended. One of the earliest fears of the health law’s supporters was that people would not pay.

Ed O’Keefe in Orlando contributed to this report.