Negotiations between GOP Sen. Lamar Alexander and Democratic Sen. Patty Murray on a bipartisan bill to stabilize the Affordable Care Act’s insurance exchanges collapsed Tuesday, Alexander said.

“Senator Murray and I had hoped to agree early this week on a limited, bipartisan plan to stabilize 2018 premiums in the individual health-insurance market that we could take to Senate leaders by the end of the month,” Alexander said in a statement. “During the last month, we have worked hard and in good faith, but we have not found the necessary consensus among Republicans and Democrats to put a bill in the Senate leaders’ hands that could be enacted.”

The announcement comes at the same time Republicans in the Senate are mounting one last effort to repeal and replace the ACA, better known as Obamacare, with what’s become known as the Graham-Cassidy-Heller-Johnson plan.

The bipartisan bill had been taking shape following a series of hearings that included state-level insurance officials, health-policy experts, and governors. The participants offered a slew of ideas to help ensure that uncertainty was stripped out of the market for 2018 and to control costs for Americans.

Insurers have cited increased political uncertainty as a factor for both increasing premiums in the Obamacare exchanges and pulling out of markets altogether. Alexander and Murray hoped to alleviate some of that uncertainty with new legislation.

Influential Republicans including White House officials and the Senate Finance chair, Orrin Hatch, came out against the Alexander-Murray push, which helped doom the effort. House Speaker Paul Ryan said his chamber would not even consider a bipartisan stabilization bill.