Who could foresee a hit?

Simon Baker is having a rough time. He’s battling a stubborn cold, and the pressures of a long shooting day on the Warner Bros. lot are taking their toll. But Baker, the star of CBS’ “The Mentalist,” still has a smile and twinkle in his eyes. That’s how it is when you’re the face of the season’s only breakout hit at a time when few believed it possible for a major network to deliver a sizable weekly audience for a new scripted program.

“Everything is good right now, really good,” said Baker, apologizing for his cough and the rasp in his voice. “Every TV show is a crapshoot, really. But every once in a while, a show gets anointed as ‘the show.’ And at the moment, we are it.”

Even up against Fox’s formidable “American Idol,” which has earned the nickname “Death Star” for obliterating the competition, “The Mentalist” has emerged as the most popular -- and most unlikely -- hit of the network TV season.

An aggressively unhip show with no built-in “water cooler” factor, “The Mentalist” might try the patience of the most seasoned psychic as to why it has triumphed over more edgy, star-driven fare. The success of the drama, which follows in the tradition of “The Rockford Files,” “Magnum P.I.” and “Columbo,” where the quirky main character solves crimes with ingenuity and more than a little humor, might come down to the adage that everything old is new again.

Not only has it outdistanced its more high-profile newcomer competition such as Fox’s “Fringe,” the CW’s “90210” and NBC’s “My Own Worst Enemy,” the Tuesday night show has accomplished the rarest of feats: being a breakout scripted hit on network TV that started strong out of the gate. Only “Desperate Housewives,” “Lost” and the fading “Heroes” have displayed similar momentum in the last several years.

The show, in which the native Australian plays a onetime psychic turned crime investigator, regularly lands in the top 10 of the week’s most-watched shows. Its first-run episodes average almost 19 million viewers per week, while even repeats bring in more than 14 million, according to Nielsen.

“This show has clearly landed above the fray of other new entries,” said Jason Mittell, an associate professor of film and media culture at Middlebury College in Vermont. “It has succeeded mostly on the backs of other CBS procedurals that are popular with older viewers. It’s less about innovation than the repetition of the formula -- with a difference.”

Baker has his own theory. “It’s a procedural, but it’s not defined by its procedural nature. It has a sly wit about it. There’s earnest moments, but it doesn’t take itself too seriously.”

While other major networks have seen viewership decline this season, CBS alone can boast an audience increase -- in no small part due to “The Mentalist.” Bouyed by the show’s strong ratings, CBS is the clear No. 1 network for total viewers. NBC and ABC have no new hits, and almost all of the midseason scripted entries have already failed.

Like many of the network’s top programs, the show is essentially a crime drama, but one that deviates in tone from its rather grim and gruesome science-heavy cousins like “CSI: Crime Scene Investigation” and “Criminal Minds.” “The Mentalist” is built upon the quick wit and sharp intellect of its hero, who wields his uncanny powers of observation like a scalpel.

“It’s in the ballpark of our other shows, but it’s slightly offbeat,” said Nina Tassler, president of CBS Entertainment. “The humor played well. We certainly knew we were on the right track. We looked at all the elements, then spread a bit of pixie dust on it.”

Peter Roth, head of Warner Bros. Television, which produces the show, said series creator Bruno Heller pitched the show this way: “What if Sherlock Holmes and Angelina Jolie had a baby and he grew up?”

Like other CBS procedurals, “The Mentalist” has a heavy female following -- almost 60% of its audience is female and 18 or older, says Nielsen.

On its face, the show’s widespread appeal might even be a mystery to Baker’s character, Patrick Jane. The show lacks the staples of many other crime dramas -- among them, a cool soundtrack, edgy fashions and fresh young stars.

But if Jane looked in the mirror, he might be able to solve much of the puzzle. Tassler, Roth and other forces behind the series say Baker’s GQ-ready looks and easygoing charm are crucial. Critics have given the series largely favorable notices, and many single out Baker’s performance. For an actor who has had plenty of ups and downs, the role fits Baker like one of his vests -- easy and relaxed.

The happily married father of three had one successful series (CBS’s “The Guardian”) and one flop (he costarred in the short-lived “Smith” with Ray Liotta). His movie track record has also been spotty -- he was the scamp who seduced Anne Hathaway in “The Devil Wears Prada,” and he was the unfailingly sweet, patient male lead in the 2006 interracial romantic comedy “Something New.” But some of his recent films (“Sex and Death 101,” “The Lodger”) had brief theatrical runs or went straight to video.

The show features little on-screen violence and only a hint of romantic tension between Baker and his costar Robin Tunney, who plays a skeptical agent with the California Bureau of Investigation. It also isn’t big on firepower -- amazingly, Baker doesn’t even carry a gun.

The setup is clear and simple, but not something audiences haven’t heard echoed in shows like “The Fugitive” and “The X-Files.” In the show, it’s the main character’s celebrity as a con man psychic that makes him the target of a psychopath who murders his family. Devastated and adrift, the man seeks redemption as a law enforcement consultant, but is still taunted by the elusive villain.

“What’s behind this is the continuing popularity of the police procedural on television,” said Tim Brooks, a former network executive and television historian. “Plus the character is very relatable. He does something that everybody wishes they could do.”

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An unassuming hit

On a recent set visit, the only hint of the show’s elevated status was the Favorite New TV Drama statuette from CBS’ “The People’s Choice Awards” planted on top of a television monitor. Otherwise, the mood was businesslike -- except for an excited group of crew members who gathered around a small TV during lunch time to watch some real drama -- a live police pursuit.

While shooting a scene with another actor in an interrogation room, Baker was mostly quiet as cameramen set up angles. But he can also be energetic and talkative, chatting up actors with only small parts between scenes and showing genuine interest in their careers.

Perched nearby on a director’s chair, Heller contemplated the success of “The Mentalist” with a mix of self-deprecation and surprise, seeming caught a little off guard by the hoopla surrounding the series. He created the show, he explained, mostly as a personal reaction to his involvement in HBO’s “Rome,” a critically acclaimed series with heavy doses of sex and violence. (He co-created the racy series about the intrigue of ancient Rome and wrote many of the episodes.)

“After going through that incredibly intense experience, I wanted to do something that was positive, that had joy in it and would make people happy and reassure them that redemption is possible,” he said. “I needed to challenge myself -- it’s easier to do something that is edgier and complex. I wanted to do a network show that could air at 9 p.m.”

Heller pitched nearly a half-dozen shows for a series, but it was “The Mentalist” that grabbed the network’s attention. The show itself was inspired by merely driving around the city.

“On every block, you can see a house or someplace where a psychic is plying his or her trade,” he said. “I presume most of these people are making a decent living -- they must be performing some sort of service. Even though they can’t talk to the dead, they must be doing something that’s therapeutic. They’re lying to people, but helping them at the same time. It’s that moral ambivalence that interested me.”

He still seems surprised by the show’s hold over such a large audience. “When you start a TV series, the degree of success it may have is the least of your priorities,” he said. “There are shows that are just great that don’t succeed. You can never predict.”

Despite conventional pressure to remain in familiar narrative territory on a network, the show is trying to avoid predictable story lines, said Heller. For instance, those fans hoping for a love connection between the show’s stars may be disappointed. It’s unlikely -- neither actor wants to explore that well-worn territory for now.

“I feel like Simon is my brother,” said Tunney. “I don’t know what would happen if we took the show down that road. I don’t feel we have to.”

Though the series appears to have momentum, Baker said the show still faces challenges. He said he, Heller and the cast need “to find out where the show lives, and to hit that mark as often as we can. We do 23 of these a year and it’s hard to get every one right. But if we can get about 18 or 19 in the zone, then I would be happy.”

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greg.braxton@latimes.com