Republicans’ years-long push to dismantle Obamacare collapsed in dramatic fashion overnight when three G.O.P. senators joined Democrats to vote against a so-called skinny repeal bill, an 11th-hour effort to keep the health-care debate alive that even Republicans admitted was a “fraud” and a “disaster.” While Republican senators Lisa Murkowski and Susan Collins had already said they would vote against the bill, it was John McCain who unexpectedly killed the legislation after 1:30 A.M. on Friday, concluding an unprecedented multi-day legislative drive in the Senate and eliciting cheers from hundreds of protesters outside the Capitol as word spread that Barack Obama’s signature health-care law would live to see another day.

For months, Mitch McConnell has struggled to unite the divisive moderate and conservative factions in his caucus around a health-care bill. Thursday, in a last-ditch attempt to fulfill his party’s pledge to repeal the Affordable Care Act, he presented a pared-down bill that would have gutted key elements of the 2010 law—including the individual and employer mandates and the requirement that states provide certain minimum benefits like maternity care—and defunded Planned Parenthood for one year. Four Republican senators, including McCain, held a press conference to denounce the bill, which they described as a disaster but announced they would vote for anyway if the House could promise that it would not actually pass it, but rather use the legislation to begin a conference negotiation between the two chambers, keeping the repeal effort alive. The bill itself, if passed into law, would have resulted in 15 million more people losing health insurance coverage in the first year alone, a spike in premiums, and chaos in the individual market, according to a last-minute analysis by the Congressional Budget Office.

While nine senators who were on the fence said they were assuaged by Speaker of the House Paul Ryan, McCain remained unconvinced. Hours later, he would cast the deciding vote against the legislation, effectively ending the latest push to repeal Obamacare and laying bare what may be an unbridgeable divide in the Republican Party.

McCain’s sudden defection capped a dramatic week for the Arizona senator, who returned to Washington earlier this week to much fanfare after he was diagnosed with brain cancer, only to be demonized by the left when he voted on a motion to proceed on the expedited repeal debate despite having just denounced that secretive process as an affront to the normal functioning of the Senate. But McCain regained his maverick bona fides on Friday when, despite last-minute pleas from Ryan, Vice President Mike Pence, and President Donald Trump, he gave a swift “no” and flashed a thumbs-down when his name was called. “I thought it was the right vote,” McCain told reporters, Politico reports. “I do my job as a senator.”

In a statement issued after the failed vote, McCain explained his thinking. “From the beginning I have believed that Obamacare should be repealed and replaced with a solution that increases competition, lowers costs, and improves care for the American people. The so-called ‘skinny repeal’ amendment the Senate voted on today would not accomplish those goals,” he said, going on to call for a bipartisan solution. “We should not make the same mistakes of the past that has led to Obamacare’s collapse.”

The failed vote on the “skinny” repeal and the string of other repeal votes before it comes as a significant rebuke to Trump, who, in need of a legislative victory, flexed his muscles from the bully pulpit to try to coerce recalcitrant senators into delivering him a win. Trump’s initial response to the vote was relatively restrained: “3 Republicans and 48 Democrats let the American people down. As I said from the beginning, let ObamaCare implode, then deal. Watch!” he tweeted.

McConnell’s reputation as a master tactician also suffered a blow. After blaming the Democrats for the failed attempt to repeal the A.C.A. he conceded, “It’s time to move on.” But the knives are already out for the majority leader. On Friday, Representative Mo Brooks called for McConnell to step down. “Unquestionably the leadership at the top is responsible. The buck stops there, that's why you take on that kind of responsibility,” the Missouri congressman said during an interview with CNN’s New Day. “It’s not necessarily anything bad about Mitch McConnell himself personally. But he’s got a job to do, and if he can't do it then, as The Apprentice would say, ‘you're fired,’ get somebody who can.”