For anyone hiding a secret, it was often said, four of the most dreaded words in the English language were “Mike Wallace is here.”

As the biggest star of the longest-running, highest-rated, most influential news show since its 1968 debut, Mr. Wallace helped define television journalism with an adversarial interviewing style that was as admired as it was feared.

From an early career as an actor, cigarette pitchman and game-show host, he transitioned to what he called a more substantial career in hard news. “60 Minutes” made him rich, famous and one of the most commanding and imitated fixtures of TV journalism for more than two generations.

Mr. Wallace, 93, died April 7 at an assisted living facility in New Canaan, Conn., CBS News announced. He had a history of heart ailments, including a triple bypass operation in 2008.

Mr. Wallace developed a compelling persona that seamlessly blended country club locker-room bonhomie with the prosecutorial zeal of Torquemada. With his theatrical baritone, he pitched softball questions that could take a sudden detour into an uncomfortable line of questioning meant to sniff out misdeeds or fun gossip.

He became known as one the most skilled interviewers of the powerful, famous and elusive — world leaders, Hollywood celebrities, controversial newsmakers, notorious criminals and the hinkiest scam artists. He was a pioneer of the surprise or “ambush” interview, a technique intended to shock its targets into spilling information they might not reveal in a scheduled interview.

In short, he helped invent magazine-style television, which merged elements of news and entertainment in a powerful and immensely profitable way that kept CBS the most formidable of network-news providers for years and “60 Minutes” one of the most trusted of news programs.

Its weekly viewership reached 40 million at the peak of network TV audiences in the early 1980s. It spawned many imitators and, like Mr. Wallace, won the top honors of the profession.

Television historian Ron Simon said Mr. Wallace’s ability to remain engaging while asking aggressive questions was crucial to his success as an investigative reporter.

“He paved the way for how investigative journalism is done on television,” said Simon, a curator at the Paley Center for Media, a New York-based museum of radio and television. “He created a persona that worked for many decades and was compelling to viewers, who identified with him and trusted him as someone representing their interests.”

When mapping out an interview, Mr. Wallace told Time magazine he organized his questions by ambition, motivation, greed, joy and defeat, and said this established a “chemistry of confidentiality” that showed his guests “I cared enough to read and look at and worry about the questions.”

Among Mr. Wallace’s memorable exchanges was a 1979 interview with Iran’s Ayatollah Ruhollah Khomeini shortly after his followers seized the U.S. Embassy in Tehran and took 52 Americans hostage.

“Imam,” Mr. Wallace began, “President Sadat of Egypt . . . says that what you are doing now is, quote, ‘a disgrace to Islam.’ And he calls you, imam, forgive me, his words, not mine, ‘a lunatic.’ “

The moment was riveting, in part because the interpreter initially refused to translate what Mr. Wallace had said. Mr. Wallace said the statement was crucial to make, to get around Khomeini’s “almost robotic” responses on questions that had been approved in advance by Iranian officials.

Khomeini called for Sadat’s “overthrow”; Sadat was killed by gunmen in 1981.

In other interviews, Mr. Wallace caused a long chill in his friendship with the Reagans when he appeared to criticize first lady Nancy Reagan for not being able to say how many blacks were on her husband’s top campaign staff.

Mr. Wallace once got a Chicago business executive keeping two sets of tax records to admit to fraud on camera. As the reporter described the story to USA Today: “I said, ‘Look, between you and me, Chicagoans do this all the time, right?’ And he says, ‘Between you and me, you’re right.’

“Between you and me and the whole middle of America! What a moment!”

Mr. Wallace said he liked constructing stories as if they were “morality plays,” and his reports developed certain hallmarks over the years: the penetrating question, the close-up so intense it showed the guest’s pores, the way he discredited a guest’s statement by repeating it back in disbelief.

In 1993, Mr. Wallace and a camera crew surprised a New Mexico priest, on a 10-mile pilgrimage, who allegedly molested a parishioner when she was 15.

The priest, Robert Kirsch, said Mr. Wallace was harassing him but the newsman persisted: “Now why would she say that about you . . . if it were not so?”

A state judge ruled against the accuser because she had waited too long to bring her claim.

Mr. Wallace himself was once asked on “60 Minutes” if he’d worry about someone barging into his office and confronting him with what appeared to be bombshell evidence.

“I wouldn’t,” joked the four-time married Wallace, “which is why I lead a life beyond reproach.”

As the decades passed, Mr. Wallace became as much a celebrity as any of the actors, presidents and dictators he profiled. His was instantly recognizable with his full, pitch-black hair raked backward, his deeply tanned skin and enviably trim physique earned from years of tennis and sit-ups.

Despite his bouts of depression, his stamina for demanding assignments and far-flung travels never waned. “I love the urgency of what we do,” he told People magazine. “I like the battles that take place, the jousting.”

He remained a competitive correspondent on “60 Minutes” well into his senior years — “60 Minutes” creator Don Hewitt once called him a “force of nature” — and he could turn brusque and demanding when he was not accorded star status on assignment choice.

Mindful of his public image, Mr. Wallace became a leading and controversial voice in the 1990s debates over corporate censorship in journalism when CBS executives interfered with his “60 Minutes” segment on a tobacco industry whistleblower.

Mr. Wallace conducted the interview with the whistleblower, Jeffrey S. Wigand, who said he could prove cigarette executives were lying when they publicly declared they knew of no evidence to prove the addictive nature of nicotine.

The segment was made just as CBS was in the middle of a takeover by the conglomerate Westinghouse, and the network feared Wigand’s confidentiality agreement with his old employer, Brown & Williamson, would make CBS susceptible to a multibillion-dollar lawsuit.

In 1995, “60 Minutes” broadcast only a small portion of Wigand’s interview and hid his identity and face. On air, Wallace noted the limitations imposed by CBS management.

But the entire behind-the-scenes drama proved damaging to the prestige of “60 Minutes” and Mr. Wallace and culminated in a Hollywood film, “The Insider” (1999), with Christopher Plummer portraying Mr. Wallace as a corporate lackey who didn’t use his authority to stand up for journalistic integrity.

Mr. Wallace denounced the film, and CBS News President Andrew Heyward said Mr. Wallace was “vociferous and public in his campaign and in his criticism of his own corporate bosses.”

Mr. Wallace lightened his opinion after the film was nominated for Academy Awards, telling a reporter, “Everybody is saying I really don’t look so bad at all in it.”

Myron Leon Wallace was born May 9, 1918, in the Boston suburb of Brookline. His parents were Russian Jews whose last name, Wallik, was changed after they arrived in the United States. His father became an insurance broker.

At the University of Michigan, Mr. Wallace became an announcer on the college radio station and said it might have been the ham in him that found radio appealing.

After graduation in 1939, he worked as a radio announcer in Michigan and Chicago doing news, soap operas and dramatic serials and served as a beauty contest emcee.

In 1940, Mr. Wallace married Norma Kaphan, his college girlfriend. They had two children, Peter and Chris, before divorcing. Mr. Wallace’s later marriages to Buff Cobb, a socialite with whom he hosted early TV talk shows, and artist Lorraine Perigord ended in divorce.

Survivors include his fourth wife, Mary Olberg Yates, whom he married in 1986, of New York City; his son Chris Wallace, a broadcast journalist who is now an anchor with Fox News, of Washington; two stepsons from his marriage to Yates, Angus Yates of Washington and Eames Yates of New York City; a stepdaughter from his marriage to Perigord, Pauline Dora of New Canaan; 11 grandchildren; and two great-grandchildren.

Mike Wallace’s early broadcast experience served him well during World War II. The Navy placed him in charge of radio entertainment at the Great Lakes Naval Training Station. Afterward, he moved into television talk and game shows and even made an “ingratiating” leading man in the Broadway comedy “Reclining Figure” (1954), according to theater critic Walter Kerr.

Mr. Wallace’s dislike for the repetition of stage work led him back to television, most notably with the program “Night Beat,” which first aired in 1956 on a DuMont Network station in New York.

Mr. Wallace worked with producer Ted Yates to create a new kind of interview show, starting with a Spartan setting that resembled a police interrogation room.

“Night Beat” guests included U.S. Communist Party leader Earl Browder, future U.S. Supreme Court justice Thurgood Marshall, author Norman Mailer and the imperial wizard of the Ku Klux Klan.

Mr. Wallace asked blunt, often uncomfortable personal questions about sex, religion, voting habits and murder. He prodded racketeer Mickey Cohen into saying: “I have killed no men that, in the first place, didn’t deserve killing.”

In 1996, Mr. Wallace told the Boston Globe that in researching people for “Night Beat,” “We used to sit around and chortle, ‘Look what this guy said five years ago, and today look what he’s doing. Let’s stick it to him!’ It’s as simple as that, I swear.”

He was called “Mike Malice” by critics who objected to his prosecutorial style. He acknowledged a fascination with “the weak spots in people” but said he chose his questions not to be mean but to trigger “a reasonable exchange of ideas.”

After “Night Beat,” Mr. Wallace hosted public affairs and game shows as well as commercials for Parliament cigarettes. He kicked around several stations and anchored the 1960 election coverage for the independent Westinghouse Broadcasting Co. He also narrated David Wolper’s syndicated and highly rated “Biography” series before joining CBS in 1963.

At the time, the so-called “Tiffany network” that had once been home to newsman Edward R. Murrow had the most prestigious pedigree. Mr. Wallace had a hard time getting anyone to take him seriously.

He later recalled: “The people at CBS said, ‘You mean to say that we’re going to have the fellow who’s measuring the quarter-inch filtered tip of the Parliament cigarettes? That’s the same guy who’s going to be measuring the missile gap? Not on CBS.’ ”

But Mr. Wallace said he was determined to change his image as a lightweight. He said he was motivated in large part by the accidental death, in 1962, of his teenage son Peter while hiking through Greece. The elder Wallace took a series of demanding assignments to prove his worth: a tour in Vietnam, on-air reporter for the “CBS Evening News” and questioner on the public-affairs show “Face the Nation.”

Then came “60 Minutes.” The show was the brainchild of visionary CBS producer Don Hewitt, who wanted to create a variation on the traditional and often ponderous hour-long news documentary. It would be sliced into three shorter segments varying between the serious and the frivolous. Hewitt joked this approach — which he dubbed “Life magazine of the air” — would cater to his own short attention span.

Hewitt cast Mr. Wallace opposite the easygoing Harry Reasoner as the news show’s first correspondents and described them as “the perfect fit — the guy you love and the guy you love to hate.”

Mr. Wallace, who officially retired in 2006, remained with the CBS news program longer than any of its other journalists, a list that over the years included Dan Rather, Diane Sawyer, Morley Safer, Ed Bradley and Harry Reasoner.

Mr. Wallace periodically attracted controversy, such as showing physician-assisted suicide advocate Jack Kevorkian giving a lethal injection to a willing patient in 1998.

“Turn it off if you don’t like it,” Mr. Wallace told such critics as Catholic leaders and media writers. “This is what death, in this particular case, looked like. Not some horror. A man was put to sleep and peacefully passed because he and his family wanted it to happen.”

Mr. Wallace said the most “traumatic” point in his career was the $120 million libel suit brought against CBS by Army Gen. William C. Westmoreland, commander of U.S. military forces in Vietnam, for a segment Mr. Wallace hosted.

The 1982 broadcast, “The Uncounted Enemy: A Vietnam Deception,” accused Westmoreland of deliberately underestimating enemy troop numbers in Vietnam. A CBS internal investigation also criticized the story, and an out-of-court settlement was reached.

Mr. Wallace said the tension amid the trial and his crumbling third marriage led to his hospitalization for exhaustion and a diagnosis of clinical depression. Shortly after, he said, he tried to kill himself with an overdose of sleeping pills.

“I was copeless. Not just hopeless, but copeless,” he told an interviewer. “I tried to keep on working because I was ashamed of acknowledging the fact that I was depressed. You don’t use that word.”

Gradually he began to speak out — on talk shows and in lecture halls — about the insecurities he felt as a result of his illness, and in 1996, he won a Harvard Medical School prize for helping remove the stigma from the mental condition.

Mr. Wallace threatened to retire but never did, saying in his 2005 memoir, “Between You and Me,” he kept getting interview “opportunities I can’t turn down.”

The interview he always wanted and never got was with Pope John Paul II. “I wanted to talk to him not just about being the pope, but about other things — about acting, about politics, about celibacy, about skiing,” he told the Newark Star-Ledger. “I wanted to talk to him as a man.”