The Senate on Tuesday voted by the narrowest margin to move forward with its Obamacare repeal push, a significant step for Republicans that still leaves senators searching for an agreement on how best to follow through on a campaign promise that has defined most of the last decade.

Vice President Mike Pence was forced to break a tie as the Senate voted 51-50 to start debate on proposals to change the landmark health-care law. The vote comes after weeks of setbacks for Republicans as party divisions stalled multiple versions of their plans to overhaul the American health-care system.

Passing the motion to proceed does not mean Republicans have a consensus on a bill they can pass. The procedural vote starts a complicated period in which senators will float varying alternatives for reshaping Obamacare.

Sens. Susan Collins, R-Maine, and Lisa Murkowski, R-Alaska, who have pushed for a bipartisan Obamacare fix, opposed the motion to proceed. The return of Sen. John McCain, R-Ariz., to the Senate on Tuesday after a surgery for a brain tumor meant it took three “no” votes to block the motion.

The Senate will navigate a complicated path to reach any agreement. One possible route could end with a so-called skinny repeal, according to NBC News, which cited two Senate sources.

The “skinny” repeal would eliminate the individual mandate penalty, the employer mandate penalty and the medical device tax, according to NBC.

But before that could happen, the Senate would “move on to debate and vote on a variety of approaches to the bill,” like the repeal now and replace later plan that key conservatives support, NBC reported. That would likely get blocked.

The chamber could then field some version of the replacement plan that stalled out recently, which may also fail, as it could require 60 votes. The vote for a partial, “skinny” repeal may follow that.

As the roll call vote was about to begin Tuesday in the Senate, at least 10 protesters in the chamber broke out in chants of “Kill the bill!” and “Shame!”

The motion’s passage came after at least three senators who previously opposed proceeding to a version of a health-care bill decided to back Tuesday’s motion: Sens. Rand Paul, R-Ky., Dean Heller, R-Nev., and Shelley Moore Captio, R-W.V.

Sen. John McCain, R-Ariz., returned to the Senate to a standing ovation just days after revealing he has a brain tumor and supported the motion to proceed. McCain criticized the process that led to the health-care bill and called for the Senate to return to the usual process like committee hearings — despite backing the Republican effort on Tuesday.

However, he added that he “will not vote for the bill as it is today.”

After the vote, President Donald Trump thanked McCain — who he called a “brave man” — for returning to cast his vote. He called the motion a “big step.”

“I want to congratulate the American people because we’re going to give you great health care,” Trump said.

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