Aetna agreed to enter the exchange as part of a contract to manage Medicaid plans in the state, she said.
Medica, one of two companies now selling individual health insurance that complies with the Affordable Care Act, said it intends to remain in the market next year.
Aetna has said it expects to lose more than $200 million on individual health plans this year in the four states where it's still selling Affordable Care Act plans. "For the consumer, they're going to see big rate hikes", Corlette said.
He added that if no companies participate in the exchange next year, it could mean that people who qualify for tax credits don't get them, although they would still have to find insurance to fulfill the individual mandate should it still be in effect.
But even if the Republicans' bill - known as the American Health Care Act - is passed by the Senate it would not solve a critical outstanding issue for insurers looking at 2018: Will the government continue to fund the cost-sharing subsidies that help individuals pay for care?
According to an Aetna spokesman, the insurer will not sell individual health plans next year in DE or Nebraska.
Carper said Aetna's withdrawal will leave a single insurer in Delaware's ACA marketplace and will force 12,000 state residents to find new coverage. But rural areas may not be attractive to insurers looking to cut losses. Some insurers have stayed in but raised the premiums they charge customers by double-digit percentages. It was the first major insurance provider to opt out of Obamacare under President Donald Trump.
While affecting only two states, Aetna's announcement quickly set off political reverberations in the charged partisan climate over whether the sprawling 2010 law should be preserved or discarded. Aetna withdrew from 11 of its 15 markets for 2017.
Blue Cross and Blue Shield of Nebraska, which stopped selling policies on the ACA exchange this year, has said it would reconsider its decision if conditions changed, but a company official said earlier this week that it has not made a decision on participation for 2018. Medica has pulled back as well, saying it may exit the program in Iowa, leaving much of the state without insurance options under Obamacare.