U.S. Sens. Susan Collins and Angus King voted with Democrats Thursday to advance an extension of Affordable Care Act tax credits that are set to expire at the end of the year.

However, the plan ultimately failed to garner enough support in the Republican-led Senate.

The Senate’s rejection of two proposals — the Democrats’ plan to extend the subsidies and an alternative from Republicans — essentially guarantees the tax credits’ expiration. Millions of Americans will see a steep increase in health care costs, including about 65,000 Maine residents who are on health insurance plans purchased through the ACA marketplace.

The issue is one that could come up on the campaign trail next year for Collins, who is expected to be in one of the most closely watched and expensive Senate races in the country in 2026.

Gov. Janet Mills, who is one of the top contenders for the Democratic nomination in that race, on Thursday blamed Collins for the expiring tax credits. The Maine Office of the Health Insurance Marketplace has previously said that without an extension of the subsidies, the average ACA premium would increase 77%.

“What Susan Collins did today is exactly what Maine people are tired of: taking votes that provide political cover after doing nothing to actually solve the problem,” Mills said in a written statement.

Graham Platner, the other leading Democratic contender, also weighed in on social media.

“I will fight tooth and nail to ensure that every Mainer has health care,” Platner wrote on X.

The Democratic proposal, which would have extended the subsidies for three years, was rejected 51-48 on a procedural motion that required 60 votes to move forward. Collins was one of four Republicans, along with Missouri Sen. Josh Hawley and Alaska Sens. Lisa Murkowski and Dan Sullivan, to vote with Democrats. King, an independent, also voted to move the proposal forward.

The Republican plan would have created new health savings accounts that would give money directly to consumers instead of to insurance companies. Democrats said the accounts wouldn’t have been enough to cover costs for most customers.

An effort to move that plan forward was also rejected 51-48 in the Senate. Collins voted for the Republican plan, while King was against it.

In a statement after the votes, Collins said that while she voted to proceed with both bills, “neither is the perfect solution to this problem.” She had filed amendments to both measures that mirror a separate bill she is working on with Republican Sen. Bernie Moreno of Ohio.

That proposal would extend the Enhanced Premium Tax Credits for two years while capping income eligibility and eliminating zero-premium plans by requiring a minimum monthly premium of $25. (Collins has said they are considering lowering the monthly premium figure to $5.)

“My votes today reflect my understanding that two things can be true at once: the Affordable Care Act has proven itself to be unaffordable; it is a broken system that must be fixed — and it cannot be fixed overnight,” Collins said in a written statement. “The families that rely on it now, however, cannot be left facing huge premium increases with inadequate assistance.”

Collins told the Press Herald earlier this week that she and Moreno were still finalizing their bill and that she hoped “serious negotiations to try and bridge the differences” between Democrats and Republicans would occur if Thursday’s votes failed.

King criticized the Republican plan that senators voted on Thursday as a “complicated proposal that will not address the impending premium increases.” He noted that he has co-sponsored legislation to permanently extend the enhanced tax credits that are set to expire.

King was key last month in helping bring about the end to a 43-day government shutdown that hinged on negotiations over the expiring health care subsidies. He joined seven Democrats who voted for compromise legislation despite calls from many members of the party to continue holding out for a guaranteed extension.

A spokesperson for King said he was not available for an interview Thursday afternoon, but he responded to a question about whether the senator regrets moving ahead with the deal.

“His voting record was consistent that he wanted the government operations to be maintained for all Mainers who rely on federal services, while at the same time placing a high priority on the bill he co-sponsored in January to extend the tax credits,” Matthew Felling said in an email.

This story contains reporting by The Associated Press.