Humana’s announcement Wednesday that it is considering raising premiums and changing or eliminating plans makes it only the latest insurer to say it might scale back involvement on the Affordable Care Act exchanges next year. Here’s the $9 billion question those insurers that remain on the ACA marketplaces ought to consider: What happens if Donald Trump is elected–and cuts off their access to ObamaCare cost-sharing subsidies?

Subsidies related to the 2010 health-care law aim to help reduce co-payments and deductibles for low-income individuals who meet certain criteria. House Republicans challenged the subsidies in court in late 2014, arguing that because the text of the Affordable Care Act does not include a specific appropriation for the subsidies, the executive branch cannot spend money Congress never disbursed.

Top Obamacare officials told a Senate panel Thursday that they can’t guarantee that the government ever will recover billions of taxpayer dollars loaned to health insurance “co-ops.”

“Today’s hearing is about the families who lost their health care plans, it’s about the taxpayers who were swindled, it’s about the bureaucrats who mismanaged this program, and it’s about the local governments who had to cut budgets from firefighters and schools to make up for Washington’s failures,” Sen. Ben Sasse, R-Neb., said.

During the hearing, held by the Permanent Subcommittee on Investigations within the Senate Homeland Security and Governmental Affairs Committee, senators paid particular attention to the 12 of 23 ObamaCare co-ops that have failed.

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Humana became the latest health insurer to serve notice that it might leave some Affordable Care Act exchanges next year, creating more uncertainty for customers ahead of this fall’s enrollment window and presidential campaign, during which the law is sure to remain a hot debate topic.

The insurer, which is being acquired by rival Aetna, said Wednesday that it expects to make a number of changes to its business for 2017, and that may include leaving some markets both on and off the exchanges or changing prices. Humana Inc. sold coverage in 15 states this year.

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House Republicans are subpoenaing documents related to ObamaCare payments that they say break the law.

Two House committees issued the subpoenas on Wednesday, saying the administration has refused to comply with document requests for over a year. The administration counters that the matter is part of an ongoing lawsuit.

“Now, 15 months after our first request, we still don’t have the most basic information about the $5 billion in unlawful payments to insurance companies,” Reps. Fred Upton (R-Mich.) and Kevin Brady (R-Texas), the chairmen of two committees, said in a statement.

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Insurers have begun to propose big premium increases for coverage next year under the 2010 health law, as some struggle to make money in a market where their costs have soared.

The companies also have detailed the challenges in their Affordable Care Act business in a round of earnings releases, the most recent of which came on Wednesday when Humana Inc. said it made a slim profit on individual plans in the first quarter, not including some administrative costs, but still expects a loss for the full year. The Louisville, Ky.-based insurer created a special reserve fund at the end of last year to account for some expected losses on its individual plans in 2016.

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