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John McCain, maverick of the Senate, did not return to Capitol Hill and suddenly stop the progress of the Republican health-care effort.

But the Arizona Republican, now battling an aggressive form of brain cancer, did use his moment in the spotlight Tuesday to deliver a sobering message to colleagues.

The Senate might be known as the world’s greatest deliberative body, McCain said, but it is not clear it deserves that reputation today. The partisanship, the gridlock and the political subterfuge have dragged down the institution, he said.

Senators’ work is “more partisan, more tribal more of the time than any other time I remember,” McCain told a rapt audience on the Senate floor. “Our deliberations can still be important and useful, but I think we’d all agree they haven’t been overburdened by greatness lately. And right now, they aren’t producing much for the American people.”

(U.S. Senate)

McCain delivered his speech after casting a vote in favor of beginning debate on the Republican health-care bill. But while his vote was critical to the success of that motion — Tuesday’s vote split the Senate 50 to 50, with Vice President Pence breaking the tie in favor of starting debate — McCain criticized Republican leaders for their lack of transparency and suggested the health-care effort might not ultimately succeed.

“We’ve tried to [amend the Affordable Care Act] by coming up with a proposal behind closed doors in consultation with the administration, then springing it on skeptical members, trying to convince them it’s better than nothing, asking us to swallow our doubts and force it past a unified opposition,” McCain said. “I don’t think that’s going to work in the end, and it probably shouldn’t.”

“Let’s trust each other,” he added. “Let’s return to regular order. We’ve been spinning our wheels on too many important issues because we keep trying to find a way to win without help from across the aisle. That’s an approach that’s been employed by both sides, mandating legislation from the top down, without any support from the other side, with all the parliamentary maneuvers that requires.”

McCain’s condition had become the latest reminder of the delicate nature of the GOP health-care effort, with questions swirling over the past 11 days about whether his absence would imperil future votes. The senator, 80, was in Phoenix recovering from surgery to remove a blood clot and considering options for treatment when he announced he would come back to Capitol Hill on Tuesday, a sign to Republican leaders they might be able to make progress on health care this week.

The diagnosis also raised some uncomfortable questions for Republican senators about their health-care proposals, some of which would make dramatic cuts to Medicaid and result in fewer people overall with health insurance. McCain is receiving medical care at the highly regarded Mayo Clinic in Phoenix, and unlike many average Americans, he is at no risk of losing his coverage or his ability to receive treatment under the GOP bills.

Just before the vote began, protesters rose up from the visitors gallery and began chanting. “Kill the bill — don’t kill us!” It took close to 90 seconds for protesters to be removed, one by one, so that the vote could continue. The shouts could be heard throughout the Senate side of the Capitol.

(U.S. Senate)

Separately, in the Hart Senate Office Building, protesters made their presence felt on several floors, attracting crowds of observers and police officers.

Anticipation for the vote and McCain’s return had started earlier in the day, with journalists, photographers and Senate interns gathering outside the senator’s office to await his arrival.

As the hours dragged on, it was unclear whether Republican leaders would have enough votes to begin the health-care debate and what they would do next if the procedural motion passed. White House chief of staff Reince Priebus and Centers for Medicare and Medicaid Services Administrator Seema Verma were spotted at the Capitol, hurrying through the hallways.

The vote was climactic, with McCain almost upstaged by Sen. Ron Johnson (R-Wis.), who did not immediately cast his vote and instead conferred with Senate Majority Leader Mitch McConnell (R-Ky.) in a passionate conversation.

McCain arrived at the Capitol around 3 p.m. with his wife, Cindy, and boarded an elevator to the second floor. Escorted by a Senate usher and police officers, he flashed a tight smile at reporters awaiting him and walked toward the chamber. Asked how he was feeling, he shook his hands in a so-so gesture, then gave a thumbs-up.

As they do for every senator, high-school-age pages opened the Senate chamber’s doors, and McCain walked through. But unlike what they do for every other senator, his colleagues turned in his direction and broke into applause.

McCain entered to a rousing ovation. He waved his arms at the clerks who record votes, and after they called his name, he flashed a thumbs-up to vote yes. Johnson immediately went to the well and also flashed a thumbs-up, providing the crucial 50th vote to allow Pence to break the tie.

Despite the hyper-partisan nature of the legislation, McCain provided a cathartic moment for the chamber. Almost every senator lined up to shake his hand and welcome him back. Senate Minority Leader Charles E. Schumer (D-N.Y.), who has become close friends with McCain in the past four years, ran up and hugged him. Sen. Elizabeth Warren (D-Mass.), a staunch liberal at odds with McCain on most policy but who recently traveled with him to Afghanistan, gave him a long, warm hug.

Democrats, though distressed by the GOP’s moves to undo one of Barack Obama’s signature domestic achievements, acknowledged the psychological lift prompted by McCain’s return.

“Anyone who thought that he had lost any integrity, all they had to do was listen to that speech,” Schumer told reporters. “I could have written the same speech — I just would have voted the other way. The idea of regular order and the idea that this bill is not a very good bill, both came out brilliantly in McCain’s speech, which was much better than any speech that any Democrat could have given.”

Sen. Richard J. Durbin (D-Ill.) said McCain’s return to the floor “was a great warm feeling” for his colleagues, adding: “Clearly, you can look at the man and know he’s been through a battle. But he’s a person who’s not afraid of a battle.”

Leaving the Capitol after his vote and speech, McCain said that he was not certain how long he would be in Washington, because of the continuing questions he faces about treatment options.

“I think by the end of the week, for sure.” he said in a brief interview. “We’ll have to figure out the rest after that. It’s a little hard to know, because we’re still looking at stuff.”

That would guarantee him enough time to finish up the health-care debate but would leave open the question of whether he could oversee debate on the Pentagon policy legislation that is next up on the calendar and which is his prerogative as chairman of the Senate Armed Services Committee.

After McCain’s speech, most Senate Democrats headed down the stairs of the Capitol to talk to protesters. There was no amplification; protesters reached over each other for photos, cheering for Democrats they recognized.

“We are going to fight and fight and fight until this bill is dead!” Schumer said.

David Weigel contributed to this report.