Sen. John McCain John Sidney McCainMomentum growing among Republicans for Supreme Court vote before Election Day McConnell urges GOP senators to 'keep your powder dry' on Supreme Court vacancy McSally says current Senate should vote on Trump nominee MORE (R-Ariz.) on Friday announced that he will vote against the latest proposal to repeal ObamaCare, potentially dooming the legislation and, with it, the GOP's last shot at passing a health-care overhaul this year.



“I cannot in good conscience vote for the Graham-Cassidy proposal. I believe we could do better working together, Republicans and Democrats, and have not yet really tried," he said in a statement, referring to the legislation spearheaded by GOP Sens. Lindsey Graham Lindsey Olin GrahamMcConnell locks down key GOP votes in Supreme Court fight Will Republicans' rank hypocrisy hinder their rush to replace Ginsburg? Momentum growing among Republicans for Supreme Court vote before Election Day MORE (S.C) and Bill Cassidy William (Bill) Morgan CassidyCoushatta tribe begins long road to recovery after Hurricane Laura Senators offer disaster tax relief bill Bottom line MORE (La.).



Republicans have been racing toward a vote on health care next week, ahead of a Sept. 30 deadline for approving the bill on a majority vote.

They had been hopeful that McCain's close friendship with Graham and the support for the bill from Arizona's governor would be enough to win him over.



McCain suggested the decision had weighed on him, adding that he takes "no pleasure" in it.



“The bill’s authors are my dear friends, and I think the world of them. I know they are acting consistently with their beliefs and sense of what is best for the country. So am I," he said.

Graham quickly weighed in on McCain's decision, saying he disagrees but their friendship will survive.

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"My friendship with John McCain is not based on how he votes but respect for how he’s lived his life and the person he is," he said on Twitter.

Graham added that "I respectfully disagree" with McCain and "intend to push forward for state-centric health care vs Washington-knows-best health care."

Cassidy said he was "disappointed" in McCain's decision but pledged that he would continue to work for families "being penalized because they can't afford insurance."



Supporters of Graham-Cassidy, which is also co-sponsored by Republican Sens. Ron Johnson Ronald (Ron) Harold JohnsonGOP set to release controversial Biden report Democrats fear Russia interference could spoil bid to retake Senate The Hill's Morning Report - Sponsored by The Air Line Pilots Association - White House moves closer to Pelosi on virus relief bill MORE (Wis.) and Dean Heller Dean Arthur HellerOn The Trail: Democrats plan to hammer Trump on Social Security, Medicare Lobbying World Democrats spend big to put Senate in play MORE (Nev.), argue that it's the GOP's last chance to keep their promise to roll back former President Obama's signature law.

The bill seeks to give more power to the states by converting dollars currently spent on ObamaCare’s subsidies and Medicaid expansion into block grants to states. The bill would also allow states to waive ObamaCare regulations, including those protecting people with pre-existing conditions from being charged higher premiums.



Though McCain's opposition doesn't formally kill the legislation, it leaves leadership with a daunting task: Winning over every other member of a caucus that includes both moderates and firebrand conservatives.



Sen. Rand Paul (R-Ky.) has already said he opposes the bill because it doesn't go far enough in repealing ObamaCare.



Other senators fear the bill's impact on state budgets and insurance coverage. Sen. Susan Collins Susan Margaret CollinsMcConnell locks down key GOP votes in Supreme Court fight Most Americans think winner of election should pick next Supreme Court justice: poll Murkowski: Supreme Court nominee should not be taken up before election MORE (R-Maine) on Friday said she is "leaning against" the bill, and several other key senators — including GOP Sen. Lisa Murkowski Lisa Ann MurkowskiMcConnell locks down key GOP votes in Supreme Court fight Most Americans think winner of election should pick next Supreme Court justice: poll Murkowski: Supreme Court nominee should not be taken up before election MORE (Alaska) — remain on the fence.



Three "no" votes would be enough to kill the legislation.



Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellOcasio-Cortez to voters: Tell McConnell 'he is playing with fire' with Ginsburg's seat McConnell locks down key GOP votes in Supreme Court fight Video shows NYC subway station renamed after Ruth Bader Ginsburg MORE (R-Ky.) earlier this week said he intends to hold a vote on Graham-Cassidy next week, but McCain's announcement throws those plans in doubt.

Sen. Joni Ernst Joni Kay ErnstPoll shows tight Senate race in Iowa Will Republicans' rank hypocrisy hinder their rush to replace Ginsburg? Momentum growing among Republicans for Supreme Court vote before Election Day MORE (R-Iowa), speaking at a town hall in Iowa City, floated that next week's vote could be pulled.

"I'll be honest, it seems unlikely that we'll be voting on this," she said, according to The Washington Post.

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Republicans had been open with their skepticism that the Graham-Cassidy legislation could get the needed 50 votes.

Sen. Chuck Grassley Charles (Chuck) Ernest GrassleyGOP set to release controversial Biden report McConnell locks down key GOP votes in Supreme Court fight Senate Republicans face tough decision on replacing Ginsburg MORE (R-Iowa) told Iowa reporters that Republicans were still at least two votes short "and I don’t see those other one or two votes coming."

And Sen. Ted Cruz Rafael (Ted) Edward CruzMurkowski: Supreme Court nominee should not be taken up before election Battle lines drawn on precedent in Supreme Court fight Sunday shows - Ruth Bader Ginsburg's death dominates MORE (R-Texas) told conservative radio host Michael Berry that "it's not clear if we're going to get to 50 votes or not."



McCain, who has brain cancer, cast the decisive vote that halted the GOP's first ObamaCare repeal effort over the summer. With a dramatic thumbs down on the Senate floor, he stopped that legislation in its tracks.



Murkowski and Collins also voted against that "skinny" repeal bill.



McCain at the time complained the legislation had been rushed to the floor without going through the normal committee process, and he leveled that same complaint against Graham-Cassidy.

— This report was updated at 3:20 p.m.