United States Senator John McCain stood with his party on Tuesday, casting a crucial vote in the Republican drive to repeal “Obamacare”, while also condemning the tribal politics besetting the nation.

Confronting an aggressive brain cancer, the 80-year-old Arizonan served notice that he would not vote for the GOP legislation as it stands now. McCain's impassioned speech held the rapt attention of his colleagues in the US Senate chamber.

“Stop listening to the bombastic loudmouths on the radio, television and the internet,” he intoned. “To hell with them! They don't want anything done for the public good. Our incapacity is their livelihood.”

A few minutes earlier, McCain had dramatically entered the chamber for the pivotal vote, his first since surgery and his cancer diagnosis in Arizona. Unified for once, Republicans and Democrats applauded and whooped for the six-term lawmaker. “Aye,” he said, thumbs up with both hands, for the GOP vote to move ahead on debate.

After he voted, McCain stood at his seat and accepted hugs and handshakes from senators in both parties, drawing laughter from the spectators' gallery when he and Vermont Senator Bernie Sanders exchanged an awkward embrace.

McCain then spoke his mind. He had a red scar and stitches above his left eye where doctors had removed a blood clot, but his voice was strong. He offered a bit of self-deprecation, saying he was “looking a little worse for wear.”

He bemoaned the lack of legislative accomplishments in the current Congress and the GOP's secretive process in working on repealing Obamacare. He issued a plea for Democrats and Republicans to work together.

Obama and the Democrats shouldn't have pushed the Affordable Care Act through on party-line votes when they controlled Washington back in 2010, McCain said, “and we shouldn't do the same with ours. Why don't we try the old way of legislating in the Senate?” That would involve committee hearings and testimony from experts and interested parties, an incremental process that could take months.

He blasted the path taken by Republican leaders “coming up with a proposal behind closed doors in consultation with the administration, then springing it on sceptical members, trying to convince them that it was better than nothing."

“I don't think that's going to work in the end, and it probably shouldn't,” he said. Debates in the Senate have become “more partisan, more tribal, more of the time than at any time I can remember,” he lamented.

With President Donald Trump threatening electoral retribution for Republicans who don't toe the line, McCain urged senators to stand up for their own constitutional status. “Whether or not we are of the same party, we are not the president's subordinates,” he said. “We are his equal!”

People with health care problems had speculated on social media how McCain would vote, and his decision disappointed many. Addressing concerns that tens of millions will lose coverage if the Republican bill becomes law, McCain said the process is far from over.

“I voted for the motion to proceed to allow debate to continue,” he said. “I will not vote for this bill as it is today. It's a shell of a bill right now.” Arizona is one of 31 American states that expanded Medicaid under former US president Barack Obama's health care law, and Republican Governor Doug Ducey is worried about tens of thousands losing their health insurance. That has to be addressed, said McCain.

The Arizona senator has emerged as one of Trump's most outspoken GOP critics. During the presidential campaign Trump had mocked McCain for his capture by the Vietnamese.

The speech on Tuesday received a standing ovation. “He's tough as a boot,” said Republican Senator John Kennedy of Louisiana. “Many people understandably would be curled up in bed in the fetal position.”

McCain's return was reminiscent of a similar scenario involving McCain's good friend, the late Democratic Senator Ted Kennedy of Massachusetts, who returned to the Senate in July 2008 while battling brain cancer to vote on Medicare legislation, his dramatic entry in the chamber eliciting cheers and applause. Kennedy died in August 2009.

McCain himself campaigned heavily on the “Obamacare” repeal issue last year as he won re-election to a sixth and almost certainly final Senate term. But he has not been a booster of the GOP health bill either.