The Senate voted Tuesday to begin debating a replacement for the Affordable Care Act. It remains uncertain as to what that replacement might look like. No formal legislation has been drafted. But senators moved to take the procedural first step, known as a “motion to proceed.” The vote was 51 to 50, with Vice President Pence casting the tie breaking vote.

Debate will now begin, most likely on a measure to fully repeal the law, also known as Obamacare.

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John McCain Makes Dramatic Return Amid Political Storm

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With 52 Republican senators, Majority Leader Mitch McConnell could afford only to lose two votes, and two GOP Senators did vote no, Maine’s Susan Collins, and Alaska’s Lisa Murkowski.

There was more drama. The vote marked the return of Sen. John McCain, the Arizona Republican whose news that he has a form of brain cancer stunned his colleagues. He was greeted with a standing ovation on the Senate floor, and was embraced by senators from both sides of the aisle. McCain then voted yes on the motion.

Before voting began, a group of protesters shouted “kill the bill’” and “shame” from the Senate’s galleries.

With debate formally opened, senators will be able to freely offer amendments, so nobody knows what the final product will look like. It’s an unusual and perhaps unprecedented way to draft a bill that will affect millions of Americans and a large chunk of the economy, to say the least.

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