"You're still an oinker," the presidential candidate told Stevens, the Alaskan renowned for legislative pork that benefits his state.
A Stevens spokesman said the gesture was taken in good humor, though McCain's crusades against federal waste have pricked Stevens before.
That is perhaps as nicely as McCain plays. The key chain incident reflects two defining characteristics of his time in Congress that some say help explain his poor showing early in the 2008 race for the White House.
FOR THE RECORD: An article published April 26, 2007, about what Sen. John McCain's reputation as a political maverick might mean for his chances in the 2008 presidential race said that President Theodore Roosevelt lost his party's nomination in the election following his second term. Roosevelt lost the nomination three years after his second term had ended.
McCain, who formally announced his candidacy Wednesday, has staked out a career in oversight, investigation, reform and old-fashioned muckraking. He has done it aggressively, sometimes with personal attacks. Careers have been destroyed in the process.
And he has often damaged the fortunes of the Republican Party. His investigation into the recent lobbying scandal helped label the Republicans as the "party of corruption" heading into the 2006 elections, in which the GOP lost control of Congress.
Though McCain's investigations have uncovered plenty of government sleaze and made him a hero to many independent-minded Americans, political historians say this barely registers on election day. Reformers have rarely ascended to the White House, analysts say, because their passions are often too narrow to galvanize voters.
Meanwhile, the pain McCain has caused fellow Republicans has cost him a reservoir of support against political headwinds -- as now, when he doggedly backs the Bush administration's policy on Iraq in the face of overwhelming voter opposition.
"You don't win a lot of votes from Republicans by investigating Republicans," observed George C. Edwards III, a political scientist at Texas A&M University. "He can't go to Republicans and say, 'There is a lot of corruption in Washington and I have been cleaning it up,' when the Republicans have been running it. That's not an applause line."
A former Navy pilot and war prisoner in North Vietnam for six years, the son and grandson of admirals, he was first elected to the House in 1982 and the Senate in 1986 in Arizona. He built a reputation as a straight shooter and staunch conservative, but one who was fiercely independent of party lines.
Early in his Senate career, McCain was one of the "Keating Five," a group of senators who were disciplined for improperly trying to influence federal regulators in the savings and loan scandal of the late 1980s. Some say this triggered his crusade against government corruption. The incident was "one of the worst experiences of my life," McCain later wrote.
Through his positions on three Senate committees, McCain has gone after a wide range of targets: the Air Force, a powerful Republican lobbyist, members of Congress, NASA officials, Firestone tires, Boeing aircraft, campaign fundraising and much more.
In the process, he has helped topple Cabinet secretaries, top military officers, a once-influential Christian conservative, Republican leaders in Congress, defense industry executives, congressional staffers and others.
"Just his name is enough to make people stand up and take notice," said Alan Ladwig, a former associate administrator of NASA. "He could make your life miserable."
Others are more severe, accusing McCain of being vindictive and manipulative in his investigations.
On the other hand, many government watchdog groups credit McCain with saving taxpayers billions of dollars, improving public safety, stopping illegal influence-peddling and protecting Indian tribes.
"He is fantastic," said Danielle Brian, executive director of the Project on Government Oversight. "It takes a special level of courage to do oversight. But it does make enemies."
Indeed, McCain the candidate doesn't tout his reform efforts, even though they are the hallmark of his political career. Reform is complicated, obscure and transitory.
"It is the nature of scandals to dissipate," said Georgetown University history professor Michael Kazin. "They don't last long enough for a candidate to base his campaign on them. They come to a head and then go away. That would be true of McCain too."
President Theodore Roosevelt is often cited as a reformer for his efforts to attack monopolies and trusts, but he gained that reputation only during his second term as president, and then lost his party's nomination in the next election, Edwards noted.
Thomas Dewey was a prosecutor who brought down the corrupt Democratic Tammany Hall machine in New York City, but lost his bid for the presidency to Harry S. Truman.
McCain has ranged far and wide. Along with attacks on corruption and government waste, he has taken aim at many traditional Republican interests.
In 2003, McCain attacked fellow Republican Sen. Pete V. Domenici's proposed funding for a uranium enrichment project in Domenici's home state of New Mexico, part of what McCain called a pork-laden energy bill. In a breach of Senate etiquette, McCain singled out Domenici's own staff director for criticism on the Senate floor. In recent years, Domenici has avoided McCain.
"Domenici and McCain hate each other," said Winslow Wheeler, a former Domenici staffer.
McCain declined to be interviewed. But in books he has written, he acknowledges his rough edges. "Although I try to refrain from being intentionally discourteous, I am demonstrative in showing my displeasure. I am often impatient and can speak and act abruptly," he wrote in "Why Courage Matters" in 2004.
Perhaps no candidate in either party has a stronger profile on national security than McCain.
"The Pentagon thinks twice what it can and can't do based on what John McCain is going to say," said James F. McGovern, a close friend, fundraiser and former Air Force secretary.
But McCain's investigations have bloodied the defense industry and the military alike. His targets have included a $1.4-million dog kennel that Stevens wanted to put on an Alaska Air Force base and a multi-year funding deal for the Air Force's front-line F-22 jet fighter.
"McCain's enemies are legion," said Loren Thompson, chief operating officer of the Lexington Institute, a public policy think tank in Arlington, Va. "Virtually every Washington office of the defense industry hates the guy."
Although the defense industry holds little power in presidential politics, most of its executives are stalwart Republicans.
Perhaps McCain's most sensational defense probe began in 2003, when he looked into an Air Force plan to lease a fleet of tanker aircraft from Boeing Co., based on its 767 jetliner.
Proponents said the existing fleet of tankers were rust buckets and that a lease deal was the only way the Air Force could afford a new fleet. An appropriations bill, pushed by Stevens, allowed the Air Force to negotiate a $23-billion leasing deal for 100 aircraft.
McCain believed the program was unnecessary, circumvented his authority on the Senate Armed Services Committee and was an egregious bailout of Boeing. Ultimately, he helped uncover what he called a sweetheart contract negotiated by a corrupt Air Force bureaucrat and her counterpart in Boeing. Both went to jail.
The collateral damage spread far and wide, taking down Air Force Secretary James G. Roche, a former personal friend of McCain's who once visited the senator in the hospital, and Marvin Sambur, an electronics industry whiz who had been recruited by the Bush administration.
At the time, Roche was due to take a new job as Army secretary. In February 2003, McCain issued a news release, saying, "God help the Army and the American taxpayer."
Roche and Sambur resigned from government service under pressure, though neither was implicated in wrongdoing. They believe McCain carried out a personal vendetta to destroy them, according to four sources who know the men. Sambur and Roche declined to comment.
At a meeting in Europe, McCain said that "Roche was a criminal and he was going to bring him down," recalled former Air Force Gen. Gregory S. Martin. "McCain and Roche didn't get along."
As for Sambur, Martin said: "He suffered the most."
Martin himself became part of the collateral damage and left the military in 2005, though he was never accused of wrongdoing. McCain "has a little less sensitivity and respect for others than I like," Martin said.
Reformers run the risk of showing favorites, and McCain's critics sometimes fault the ex-Navy pilot for picking his defense targets carefully, sparing the Navy and federal programs in Arizona.
In 1989, Rep. John D. Dingell (D-Mich.), the dean of muckrakers in Congress, launched an attack on the Army's Apache helicopter, which is made in Mesa, Ariz. It ranks as one of the biggest defense programs in McCain's state.
Dingell uncovered a memo written by an Army helicopter pilot who said he'd rather go to war with his 1960s-vintage choppers than with the new Apache, because it was so unreliable. Dingell ordered the General Accounting Office to conduct an investigation into the $13.6-billion helicopter program.
"The reliability was so bad ... that we recommended they cancel the last two production lots and use the money to fix the problems," said Jim Schaefer, author of the report.
Not long afterward, McCain went on the attack -- in defense of the Apache. He unsuccessfully pushed a five-year buying plan that would have increased production by more than 200 helicopters. It was the kind of plan that McCain would later oppose on other weapons contracts.
"The noncombatant guys with the green eyeshades can do whatever they want to," McCain was quoted saying in 1991. "The fact is the weapons system is performing superbly."
More recently, McCain helped deliver the worst black eye for the Republican Party in many years.
After published reports in 2004 disclosed that Republican lobbyist Jack Abramoff had bilked Indian tribes of millions of dollars in lobbying for tribal gambling operations, McCain launched an investigation as chairman of the Senate Committee on Indian Affairs.
From the start, he and his staff knew that the probe could lead to Republican members of Congress, including then-House Majority Leader Tom DeLay (R- Texas).
After five high-profile hearings, McCain's committee found that Abramoff and his partners had collected $66 million from Indian tribes across the nation. When the dust settled, a weakened DeLay gave up his House seat, more than eight others were convicted or pleaded guilty to criminal charges, and still others resigned from office. All were Republicans.
Samuel Popkin, a professor at UC San Diego, said McCain's investigation, while helping to stop the abuse of Indian tribes, also neutralized some of the enemies McCain would face in the current presidential race.
"The Abramoff investigation was a real shot across the bow of Christian conservatives," Popkin said.
Ever since his bid for the Republican nomination in 2000, McCain has had a troubled relationship with Christian conservative groups. In the Abramoff investigation, McCain disclosed that conservative Christian leader Ralph Reed had received about $4 million to help shut down an Indian casino in Texas, paid by another tribe that wanted to squelch competition. Last year, Reed lost the Georgia Republican primary for lieutenant governor after his opponent hammered away at the Abramoff connection.
"I think the Abramoff scandal was part of the dissolution of the power of the religious right," Popkin said.
Social conservatives still have a troubled relationship with McCain, said Family Research Council President Tony Perkins. They "may forgive but they will not forget" McCain's record, Perkins said.
The investigation also disclosed that Americans for Tax Reform, headed by influential conservative Grover Norquist, was used by Abramoff to transfer hundreds of thousands of dollars from Indian clients, though Norquist was never charged with any wrongdoing.
Yet another McCain initiative -- campaign finance reform -- also irked conservatives.
After fighting since the late 1990s to reform the nation's campaign finance laws, McCain succeeded with political ally Sen. Russell D. Feingold (D-Wis.) in 2002. The McCain-Feingold legislation banned uncapped corporate, union and other contributions to political parties. But it opened the way for a new breed of nonprofit corporation to conduct political advertising.
The legislation is deeply resented by many conservative groups, which say it restricts free speech and undermines the fundraising advantages that Republicans had over Democrats.
"It was a violation of the 1st Amendment rights of the modern conservative movement," Norquist said. "He made it hard for the National Rifle Assn. and the right-to-life groups. And he has reacted poorly to the criticism. He has yelled at me."
Other critics of McCain-Feingold question the very motives of the authors.
"The bill was largely designed to cement the control of incumbents, and that is the effect it has had," said Bradley A. Smith, a law professor at Capital University Law School in Columbus, Ohio, and former Federal Election Commission chairman.
Smith believes the bill helped shape McCain's image as a reformer and political outsider, which should appeal to the broad public. But many analysts say only political buffs care about campaign finance reform.
"Polls only show that 5% of the public feel it is important," said historian Kazin. "It is just too complicated."