The Senate on Wednesday knocked down a proposal to repeal parts of the Affordable Care Act without an immediate replacement amid a chaotic string of health-care votes this week.

The amendment failed by a 45-55 margin, with seven Republican senators voting against it: Lamar Alexander of Tennessee, Shelley Moore Capito of West Virginia, Susan Collins of Maine, Dean Heller of Nevada, John McCain of Arizona, Lisa Murkowski of Alaska and Rob Portman of Ohio.

The vote comes amid a frantic period of debate and votes this week in the Senate as Republicans push to approve some form of Obamacare repeal. Senate Majority Leader Mitch McConnell hopes the chamber can finish work on a bill by the end of the week.

Later Wednesday, the Senate voted down two more proposals related to health care.

The first was a motion to send the bill back to committee to strike provisions that would harm individuals with disabilities. It failed 48-51 along party lines with Republican Sen. Ron Johnson missing the vote.

Only 10 senators voted for the second measure, a symbolic proposal known as the Heller amendment. It was intended to express a commitment to elements of existing law that allowed states to expand Medicaid to cover more people.

GOP senators voted Tuesday by the narrowest margin to start debate on possible options to overhaul the American health-care system and follow through on a key campaign promise that has marked most of the last decade. Party divisions and skepticism from both the conservative and more moderate sides of the GOP stalled multiple pushes to repeal Obamacare in recent weeks.

On Tuesday night, the Senate voted down a procedural measure seen as a proxy to gauge support for an Obamacare repeal-and-replacement plan that stalled out in the Senate in recent weeks. Nine Republicans opposed the measure, meaning it fell well short of the votes needed for approval.

A separate Democratic amendment to send the health-care plan to the Senate committees with instructions to shield the Medicaid program from cuts failed by a 48-52 party-line vote.

The "clean" repeal proposal the Senate rejected would have rolled back parts of the Affordable Care Act and implemented a two-year transition period for lawmakers to find a replacement. It is based on a plan that Congress passed in 2015 knowing that it would face President Barack Obama's veto.

Collins was the only current Republican senator to oppose the 2015 bill. Every other GOP senator who voted against the provision Wednesday supported the 2015 repeal proposal.

More moderate GOP senators have said they fear repealing without an immediate replacement because it could generate even more uncertainty in the American insurance market. The nonpartisan Congressional Budget Office estimated repealing without an immediate replacement would lead to 32 million more Americans uninsured by 2026 and cause average premiums to double.