Sen. Susan Collins, R-Maine, arrives at the Capitol as Congress prepares to vote on the biggest reshaping of the U.S. tax code in three decades, on Capitol Hill, Tuesday.

WASHINGTON — Two Republican senators abandoned their fight Wednesday for legislation this year to help contain premium costs by resuming federal subsidies to insurers, as Congress dealt a pair of blows to President Barack Obama’s health care law.

Sens. Susan Collins of Maine and Tennessee’s Lamar Alexander ran into opposition from both parties to inserting the language into a must-pass bill preventing a weekend federal shutdown. They said they’d pursue the effort early next year, though there is no guarantee it would succeed.

The retreat was particularly embarrassing for the moderate Collins, who premised her vote for the GOP tax bill on what she said were promises from Senate Majority Leader Mitch McConnell, R-Ky., to pass legislation this year renewing the subsidies and support from President Donald Trump.

Last week, she told reporters she believed those agreements would be honored, adding, “All you cynics in the press will have to be eating crow come Dec. 31.”

Collins had to backtrack Wednesday, saying in a written statement with Alexander they had “every reason to believe that these important provisions can and will be delivered” in January as part of a bipartisan accord on long-term budget and other lingering health care measures.

Congress cleared the $1.5 trillion tax legislation on Wednesday. It delivered another swipe at Obama’s 2010 law, abolishing tax penalties it imposes on people who don’t buy insurance. Those fines are aimed at prodding healthy people to buy coverage, which helps curb premium costs for everyone.

The government payments backed by Collins and Alexander reimburse carriers for subsidizing out-of-pocket costs like co-payments and deductibles for around 6 million lower-income people. Obama’s law requires insurers to reduce those customers’ costs and has required the government to repay the carriers, costing about $7 billion this year.

After a federal judge ruled that Congress hadn’t constitutionally approved paying those subsidies, Trump halted them in October as part of his effort to weaken Obama’s law.

Alexander and Sen. Patty Murray, D-Wash., quickly produced a bipartisan bill restoring the money and giving states more flexibility to institute some “ObamaCare” requirements. The bill stalled, but Collins and Alexander were hoping it could be revived this week in a bill congressional leaders hope to approve preventing a partial federal shutdown on Saturday and temporarily financing the government into January.

But conservatives who oppose buttressing Obama’s law have long fought reviving the payments. Their opposition has always raised doubts that GOP leaders could push the measure through the Senate, despite McConnell’s promises.

And while Democrats originally backed the Alexander-Murray bill, they dropped their support when Republicans added language to the tax bill repealing Obama’s penalties on people who don’t buy insurance. They’ve not wanted to ease the political pain they say Republicans will suffer for steps that will increase customers’ premiums.

The nonpartisan Congressional Budget Office has said repealing the “ObamaCare” penalty will produce 13 million additional uninsured people and push premiums higher by an average of 10 percent.

Collins favors legislation to set up funds to help insurers reduce costs for customers with serious, costly illnesses.