McCain torpedoed the last GOP bill in July, returning to the Senate after being diagnosed with brain cancer only to cast a surprising and dramatic 50th vote against a limited-repeal of Obamacare offered by Majority Leader Mitch McConnell. But until Friday afternoon, he was officially undecided on the Graham-Cassidy proposal, apparently torn between his disgust for the party’s rushed, partisan legislative process and his famously close friendship with Graham, its most vocal salesman.

“I would consider supporting legislation similar to that offered by my friends Senators Graham and Cassidy were it the product of extensive hearings, debate, and amendment,” McCain said in a lengthy written statement. “But that has not been the case. Instead, the specter of September 30th budget reconciliation deadline has hung over this entire process.”

He continued:

We should not be content to pass health-care legislation on a party-line basis, as Democrats did when they rammed Obamacare through Congress in 2009. If we do so, our success could be as short-lived as theirs when the political winds shift, as they regularly do. The issue is too important, and too many lives are at risk, for us to leave the American people guessing from one election to the next whether and how they will acquire health insurance. A bill of this impact requires a bipartisan approach. … 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. Nor could I support it without knowing how much it will cost, how it will effect insurance premiums, and how many people will be helped or hurt by it. Without a full CBO score, which won’t be available by the end of the month, we won’t have reliable answers to any of those questions.

McCain acknowledged that his friendship with Graham put him in a difficult spot. “I take no pleasure in announcing my opposition. Far from it,” he said. “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.”

The Graham-Cassidy bill had gained momentum rapidly after its authors introduced it last week, as Republican leaders seized on one final chance to keep the repeal-and-replace promise they had been making to conservative voters for seven years. The legislation was in some ways more modest than previous Obamacare repeal proposals, as it kept most of the tax increases Democrats used to pay for the 2010 law and converted the revenue into block grants for the states. But it went further in other respects by allowing states broad latitude to opt out of the laws core consumer protections, such as requiring insurers to cover “essential health benefits” and forbidding them from charging higher rates to people with preexisting conditions.