WASHINGTON – By a narrow margin, Senate Republicans cast a pivotal vote Tuesday to begin wide-ranging debate on legislation to repeal or replace the Affordable Care Act also known as Obamacare.

The partisan 51-50 vote, with Vice President Mike Pence breaking a tie, scored a victory for Senate Majority Leader Mitch McConnell of Kentucky, but counts only as the opening salvo in the critical decision over whether to dump Obamacare, replace some of it or do nothing.

GOP Sen. John McCain of Arizona made a dramatic return to the Senate from brain cancer surgery to vote in favor of the procedural motion to debate health care. He was loudly applauded by lawmakers of both parties upon entering the chamber.

Republican Sens. Susan Collins of Maine and Lisa Murkowski of Alaska were the only GOP votes against the motion to finally debate and decide the fate of the nation’s health care system.

Previous Republican holdouts – notably Sens. Shelley Moore Capito of West Virginia and Rob Portman of Ohio – acceded to the pressure of President Donald Trump and Republican leaders to let the entire Senate decide the issue.

Democrats stuck together and opposed the motion on the grounds no good could come to Americans from the Republican effort to undo Obamacare.

Details of what bill will be debated or eventually subject to a final vote remained uncertain. Republican proposals have varied from replacing and repealing Obamacare, to modifying parts of the law, to scraping it completely and starting from scratch.

Republican leaders floated a new idea Tuesday described as “skinny repeal.” It would repeal the requirement that all Americans have insurance coverage or pay a penalty and eliminate the tax on medical devices but otherwise leave major provisions of Obamacare in place.