He's been dubbed "Senator Hothead" by more than one publication, but he's also had some success extracting his hatchet from several foreheads.
Even his Republican Senate colleagues are not spared his sharp tongue.
"F--- you," he shouted at Texas Sen. John Cornyn last year.
"Only an a------ would put together a budget like this," he told the former Budget Committee chairman, Sen. Pete Domenici, in 1999.
"I'm calling you a f------ jerk!" he once retorted to Iowa Sen. Chuck Grassley.
With Cornyn, he smoothed things over quickly. The two argued during a meeting on immigration legislation; Cornyn complained that McCain seemed to parachute in during the final stages of negotiations. "F--- you. I know more about this than anyone else in the room," McCain reportedly shouted.
Cornyn chuckled at the memory of what he called McCain's "aggressive expressions of differences." The Texan has endorsed McCain.
"He almost immediately apologized to me," Cornyn said last week. "I accepted his apology, and as far as I'm concerned, we've moved on down the road."
The political landscape in Arizona, McCain's home state, is littered with those who have incurred his wrath. Former Gov. Jane Hull pretended to hold a telephone receiver away from her ear to demonstrate a typical outburst from McCain in a 1999 interview with The New York Times.
McCain has even blown up at volunteers and, on occasion, the average Joe.
He often pokes fun at his reputation: "Thanks for the question, you little jerk," he said last year to a New Hampshire high school student wondering if McCain, at 71, was too old to be president.
Other times, his ire is all too real. This has prompted questions about whether his temperament is suited to the office of commander-in-chief or whether it might handicap him in a presidential campaign against either Barack Obama or Hillary Rodham Clinton, who are not known for such outbursts.
"I decided I didn't want this guy anywhere near a trigger," Domenici told Newsweek in 2000.
His irascibility fits with McCain's proud image as a straight talker willing to say what people don't want to hear.
Yet McCain's temper hinders his efforts to make peace with his critics and rally Republicans behind his candidacy for president. That could be a big problem, because his most persistent foes -- conservative radio hosts like Rush Limbaugh and Focus on the Family founder James Dobson -- talk to tens of millions of people each day.
McCain and his advisers insist the acrimony is about matters of policy: "We have disagreements on specific issues from time to time," McCain recently said of his critics.
In fact, the disputes often are as much about style as they are about substance.
McCain's tone was certainly on Dobson's mind when he issued a stinging anti-endorsement on Super Tuesday. He mentioned various issues, but Dobson also said the senator "has a legendary temper and often uses foul and obscene language."
Privately, some conservatives grouse that McCain can seem more convivial toward his liberal colleagues. Just last week, McCain had an animated conversation and shared a belly laugh with liberal Democratic Sen. Ted Kennedy, his partner on controversial immigration reforms, on the Senate floor.
And then there is his choice of words -- not just the expletives, but also the use of dismissive phrases such as "agents of intolerance" to describe televangelists Pat Robertson and Jerry Falwell during the 2000 presidential campaign.
Yet McCain reconciled with Falwell before his death in 2007 and has done so with many others.
McCain has also smoothed things over with Sen. Thad Cochran, who had said very recently that the idea of McCain as GOP nominee sent a chill down his spine. McCain has battled for years with the Mississippi Republican, a senior member of the Senate Appropriations Committee, over pet projects or "earmarks" inserted by committee members into spending bills.
On the Senate floor last Tuesday, Cochran greeted McCain warmly, with a broad smile and a hug.
Grassley described his relations with McCain as "friendly, but not close."
"John's a person that I have a lot of disagreements with, but you've got to have a lot of respect for him," Grassley told reporters recently. "For what he's done to defend freedom, as a Navy pilot and as a POW, you've got to have a lot of respect for him for sticking to his guns, being way out ahead of the president that the policy needed to change in Iraq."
"I'm not speaking as if I'm a born-again supporter of John McCain, I'm just trying to express it the way that I see him, and maybe some aspects of him being a good president," Grassley said.
McCain's defenders are weary of talk about his temperament. They point out that for all the decorum of the Senate, many members are known for raging at colleagues or even throwing shoes and other objects at aides.
For that matter, Dobson, the Focus on the Family founder so concerned about McCain's "legendary temper," apparently has a temper of his own. "He once berated one of our staffers to tears because he simply had to wait a few minutes to see the member," said a Capitol Hill aide who requested anonymity out of deference to his boss. Another aide said he witnessed the scene.
Since he rolled up big victories on Super Tuesday and forced his main rival, Mitt Romney, from the race, McCain has worked quickly to win over his enemies.
He delivered a well-received speech at the annual Conservative Political Action Conference in Washington, and he met last week with some of his biggest congressional foes, the uniformly conservative House Republican leadership.
Progress won't happen overnight, said conservative Republican strategist Greg Mueller.
"I hope they'll be resolved by the time we all go to convention, but it's going to take a while to mend some of the wounds and get everybody back together," Mueller said.
