https://defector.com/the-rockford-files-remains-one-of-televisions-greatest-hangs

At the same time, Rockford can feel surprisingly modern. The most striking example of this is in its depiction of policing.

What made the TV series "The Rockford Files" such a hit? (https://www.quora.com/What-made-the-TV-series-The-Rockford-Files-such-a-hit/answer/FeverIndex)

Before The Rockford Files, TV detectives were slick, wealthy tough guys. Jim Rockford was an ex-con who lived in a Malibu beach parking lot, kept his gun in a cookie jar, and often ended up broke.

Created by Roy Huggins and Stephen J. Cannell, the series succeeded by systematically inverting the hardboiled detective formula. Rockford was a reluctant hero. He took cases the police had already closed, hated physical confrontations (often bruising his hand when he did throw a punch), and frequently ended episodes arrested or beaten up. To get information, he didn't torture suspects; he kept a small printing press in the back of his car to run off fake business cards, conning his way into corporate offices by pretending to be an insurance adjuster or a government inspector.

The show worked because of James Garner's weary, everyman charm. He played Rockford with a cynical edge that never eclipsed his underlying decency. Garner made audiences root for a guy who was highly capable but constantly exasperated by the world's endless supply of grifters, bureaucrats, and deadbeats.

The supporting cast further grounded the show in a gritty, working-class reality. Instead of loyal, highly trained sidekicks, Rockford was surrounded by people who only complicated his life. His father, Rocky, constantly nagged him to quit the PI business and drive a truck. His former prison cellmate, Angel Martin, was a cowardly, pathological liar who routinely sold Jim out to save his own skin. Even his LAPD contact, Sergeant Dennis Becker, was just an overworked cop stressed out by his mortgage and irritated by Jim constantly interfering in his investigations.

The Rockford Files also established cultural touchstones that gave it an unmistakable identity. Every episode opened with a different gag message on Jim's answering machine—a novel piece of technology in 1974—setting a comedic, put-upon tone before the story even started. The Mike Post theme song, featuring a bluesy harmonica over a Moog synthesizer, became a Billboard Top 10 hit. And when Rockford did have to get out of trouble, he relied on his gold Pontiac Firebird Esprit, popularizing the 'Rockford Turn'—a high-speed reverse J-turn that Garner frequently performed himself.