Senator Marco Rubio (R-FL) and 13 other GOP senators sent House Speaker John Boehner (R-OH) a letter this week urging him to block $1 billion in funding for a key Obamacare provision needed to stabilize the health insurance market, Roll Call first reported.

When lawmakers return to Washington after the midterms, they’ll have about a month to pass a stopgap-spending bill to keep the government afloat past December 11, when the existing continuing resolution expires. The senators want the spending measure to exclude Obamacare’s risk corridor provision, which helps insurers keep policy costs low.

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Insurers who agree to sell policies on the new exchanges are reimbursed by the federal government if they incur heavy losses during the first few years of the law’s implementation.

If Republicans won’t fund the program, which is crucial to the law, it could set up another shutdown showdown – just in time for the holidays.

Many GOP lawmakers have labeled the risk corridors “a bailout for insurance companies.” Sen. Rubio sponsored a bill to repeal the program earlier this year, and in the letter sent this week, he and the other senators said that they were acting “to protect Congress’ power of the purse and prohibit the Obama administration from dispersing unlawful risk corridor payments providing for an Obamacare taxpayer bailout.”

The senators’ letter comes after a legal opinion by the Government Accountability Office revealed the law’s language does not give the Department of Health and Human Services legal authority to fund the program. So Congress must get involved.

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“Without that appropriation, any money spent to cover insurance company losses under the risk corridor program would be unlawful,” the Republican senators said in the letter. “Unfortunately, President Obama and his administration have exhibited their intent to disregard the law and ignore the Constitution.”



Still, administration officials seem confident that the GAO’s findings won’t be a problem for the program, at least not in the near future.

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HHS Secretary Sylvia Burwell, in a press briefing Thursday, dismissed the potential threat from Congress, saying, “We don’t have concerns in the upcoming year. I don’t think it’s a question that will need to be faced in 2015.”

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