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.
For The Record
Los Angeles Times Wednesday May 02, 2007 Home Edition Main News Part A Page 2 National Desk 1 inches; 56 words Type of Material: Correction
Presidential politics: An article Thursday in Section A 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.
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.