With a deep-red scar etched from his eyebrow to his temple, the legacy of brain surgery less than two weeks ago, McCain beseeched his colleagues to forsake political tribalism and restore the chamber to a spirit of compromise that had helped forge national greatness.
McCain had flown directly from his home state of Arizona to cast a crucial vote to allow a debate on a health care reform drive to proceed, but he warned that he would not vote to pass the divisive bill in its current form.
"We're getting nothing done, my friends. We're getting nothing done," he said, arguing that both sides were to blame for polarizing the process of making laws and funding the government.
"Our deliberations today ... are more partisan, more tribal ... (than) at any time than I can remember. They haven't been overburdened by greatness lately," he said, offering a lesson of civics and civility as his fellow senators unusually packed the chamber and watched from their desks with rapt attention.
The 80-year-old McCain had been welcomed back to the Senate for the first time since his devastating brain cancer diagnosis with a standing ovation, following an outpouring of goodwill toward him from across the nation. He was mobbed by colleagues, Republicans and Democrats alike, in a rare show of shared bipartisan sentiment.
It was a speech that harkened back to a forgotten and perhaps mythical age of compromise and comity in the Senate, reminding the nation of the bedrock importance of its founding political principles at a moment of extreme national political stress and recrimination.
True to his reputation, McCain scolded Democrats and Republicans alike, but he also admitted that at times he had erred himself by prizing political victories above the common good. He said both sides had erred by trying to remake health care on a purely partisan basis, and without open debate.
"I don't think that is going to work in the end, and it probably shouldn't," he said in remarks that will be tough to swallow for his own party's leadership.
McCain bemoaned the tone of modern politics, suggesting that wild partisanship was paralyzing the country's political institutions and tearing the country apart.
"Stop listening to the bombastic loudmouths on the radio and the television and the Internet. To hell with them. They don't want anything done for the public good -- our incapacity is their livelihood. Let's trust each other. Let's return to regular order."
And at a time when President Donald Trump is sowing political discombobulation in Washington with his unorthodox and disruptive leadership style, McCain reminded his colleagues they are a check on executive power.
"We are not the President's subordinates," McCain said. "We are his equals."
McCain's sermon was lent added poignancy and urgency by his illness. He was diagnosed with a malignant glioblastoma tumor, an aggressive form of cancer last week, days after an operation to remove a blood clot from his brain.
As he spoke, his wife Cindy sat alone in the public gallery, dabbing her eyes with a tissue and trying to hold back tears. Average survival for the condition tends to be around 14 months with treatment, that includes chemotherapy and radiation.
McCain said he planned to spend a few days in the Senate to help shepherd a major defense bill that is a product of his Armed Services Committee, before returning home for treatment. But he promised to be back in Washington to ensure that his sparring partners regret the kind words they had offered him.
But the very fact that he returned to vote to advance a health care bill that Democrats warn will deprive millions of Americans of coverage was a reminder that for all his deep friendships across the aisle in the Senate, the Arizona senator's staunch conservatism has rarely wavered. Some critics outside the chamber went as far as accusing McCain of hypocrisy after taking advantage of his own health coverage while weighing in on a bill that could deprive some people of theirs.
"Thankfully John McCain had access to the best health care in the world so he could get back to DC to vote to rip care away from millions," tweeted Alex Morash
, a writer with the progressive Media Matters for America watchdog group.
David Sirota, a contributor to the Young Turks Network wrote, also on Twitter
: "Next edition of Hunger Games: media & politicians in The Capitol fawn over a sick senator who votes to strip healthcare from Panem's serfs."
McCain, however, finished his speech by saying that after a lifetime as a Navy pilot, Vietnam prisoner of war, lawmaker and twice-defeated presidential candidate, being a senator is the most important job he's ever had.
"The success of the Senate is important to the continued success of America," he lectured.
"This country -- this big, boisterous, brawling, intemperate, restless, striving, daring, beautiful, bountiful, great, good and magnificent country needs us to help it thrive."
"We are the servants of a great nation."
'We don't hide behind walls, we bridge them, we are a blessing to humanity."