A number of insurers have sued the administration for not delivering risk corridor payments that the insurers argue were due to them. The Centers for Medicare and Medicaid Services announced recently that it is willing to entertain settlements, a claim that Republicans say would violate legislation approved by Congress that cut off funding to the risk corridor program, which they have derided as a "bailout" to insurance companies.

On Tuesday, reports the Hill, the House Energy and Commerce Committee sent letters to insurance companies enquiring about any communication they have had with administration officials over possible settlements.

Another letter signed by 46 Republican members of Congress was sent to Health and Human Services Secretary Sylvia Burwell and threatened legal action against the administration if it approved any settlements.

"Should the administration seek to make settlements in any pending lawsuits regarding risk corridors payments, we remain committed to exhausting all legislative and judicial options to ensure the power of the purse vested in Congress under the Constitution is respected and maintained," the letter said.

What the administration is doing

In remarks to a group of insurers on Wednesday, Burwell did not comment on the lawsuits, or the future of the risk corridor program.

Instead, Burwell emphasized the measures the administration is taking to try to improve the marketplace and make it easier for insurers to turn a profit off ACA plans. She highlighted, for instance, the stricter standards it has set for "special enrollment periods," which insurers say people have abused to sign up for insurance outside of the open enrollment period.

"We want to make sure that issuers like you can sustainably serve every type of customer," Burwell said, according to the Hill. "We also want to make sure that those who take on the highest-risk enrollees get the compensation that they need."

The administration is undertaking major marketing efforts to get young people to sign up for insurance. In addition to millennial-targeted advertising online and enrollment events held at pizza joints and bars, the Department of Health and Human Services has said it will try to connect directly with young people whose tax records indicate they paid a penalty this year for lacking insurance.

President Obama has conceded that the law must be improved to survive, a feat that will prove challenging in the coming years, given that Republicans in Congress have shown little interest in making fixes to a law they detest.

Some Democrats have highlighted the individual marketplace's struggle — which stands in contrast to the relative success of the Medicaid expansion — as evidence that the country must embrace a public option.

"Supporters of the public option warned that private insurance companies could not be trusted to provide reliable coverage or control costs," Richard J. Kirsch, a health care activist who pushed for approval of the ACA, told the New York Times. "The shrinking number of health insurers is proof that these warnings were spot on."