While Mr. Carson was a perfectionist who make life difficult for those who worked with him, Mr. McMahon said in repeated interviews over the years that his job as sidekick was “the world’s greatest job.” “You can’t imagine hooking up with a guy like Carson,” Mr. McMahon said a 1993 Associated Press interview. “There’s the old phrase, hook your wagon to a star. I hitched my wagon to a great star.”

There was nothing flashy about McMahon in his role as second banana on The Tonight Show, but that was just the point — he was supposed to be the Average Joe, looking on with admiration at the wit and dazzle of the star, and occasionally feeding the star a line or two that would make Mr. Carson look ever better.

Make no mistake about it, part of the job was also to be the butt of jokes made by Mr. Carson as he and Mr. McMahon bantered at the desk after the comic’s opening monologue. A recurring line of “comedy” was that Mr. McMahon drank too much. Often when his side kick was talking, Carson would look at the camera and raise an invisible glass to his lips. The gesture always resulted in laughs. Such was the mind set of the late night TV audience — and much of mainstream America — in the 1960s and ’70s heyday of The Tonight Show.

But if the job involved a bit of abuse, it also paid very well. Mr. McMahon was said to be making more than $4 million a year during the last decade on the air with Mr. Carson. Despite such earning power and a post-Tonight-Show pitchman and talent show host that kept Mr. McMahon in America’s living rooms well into the New Millennium, he was deeply in debt and in danger of losing his home in recent years.

Mr. McMahon blamed his debts in part on two divorces, but even that seemed more like recycled Tonight Show couch talk than truth; another of the recurring comic bits at the late night desk was Mr. Carson’s many divorces and the fortune his ex-wives were costing him. Being divorced and supporting ex-wives was part of the code of masculinity they promulgated in latenight TV.

If he embodied some of the less attractive values of his era, he also personified some of the best. The TV persona of Mr. McMahon as an everyday guy was built on some truth — as a person, he was very much a man of his Greatest Generation era.

Born in Detroit in 1923, he was raised in The Great Depression. His father has been variously described as a struggling vaudeville performer, salesman, pitchman and conman. Whatever the truth, Mr. McMahon’s family often moved, and later in life, the performer claimed to have attended 15 different schools as a child.

Mr. McMahon would later work his way through college during the summers as a carnival barker. He graduated from Catholic University in 1949. He served as a Marine flight instructor during World War II, and then re-enlisted and flew 85 combat missions as a pilot during the Korean War.

His big sturdy physique and that military history, which was known to most of The Tonight Show audience, were very much part of his on-air image. He also subscribed to a work ethic that resulted in him rarely being absent from Carson’s couch. It is said he claimed only four sick days in 30 years at NBC.

Mr. McMahon was working in local TV in Philadelphia when Carson summoned him to be second banana on the Who Do You Trust? quiz show in ABC in 1958. When Mr. Carson got the call to host The Tonight Show in 1962, he took Mr. McMahon with him. They would come to rule the late night roost for three decades knocking off challenger after challenger on the other networks.

Testament to Mr. McMahon’s talent, he did find show business life after The Tonight Show. He served as host of Star Search from 1983 to 1995 — a talent show that reached back to the Ted Mack Amateur Hour and anticipated American Idol in its competition, voting, judges and discovery of unknown talent. America’s Got Talent, which begins a new season this week, is a direct descendant.

Mr. McMahon was both genial host and father figure to the contestants. Harking back to his youthful summers as a carnival barker, McMahon during this period, also became one of the most ever-present pitchmen in the history of television. From American Family Publishers Clearinghouse to Budweiser Beer, he seemed to be everywhere on the tube selling everything. As the products became cheaper, so was his image cheapened.

While it was intended to be funny, there was something sad about his appearance in a cash-for-gold advertisement that aired during last year’s Super Bowl. At the end, his financial difficulties were massive. A fall in 2007, led to a broken neck and huge medical expenses, according to McMahon.

 In 2008, he defaulted on mortgage payments for his $4.8 million Beverly Hills home and was on the verge of foreclosure before a group that included Donald Trump bailed him out. Mr. McMahon was also involved in a series of highly publicized lawsuits.

In 2007, he sued Cedars-Sinai Medical Center over his treatment after the fall that resulted in his neck injury. He said the medical facility misdiagnosed the injury and then did two faulty surgeries. He had previously sued various contractors claiming he and family members were sickened by toxic mold in his house.

Near the end, it was more often than not distressing to see Mr. McMahon, the man who had once brought smiles to so many faces, on TV. He appeared usually in diminished circumstances and for the wrong reasons.

Mr. McMahon is survived by his third wife, Pamela Hurn, whom he married in 1992, and by five children. A sixth died in 2005.