If you enjoyed seasons two through seven of the 1980s police procedural Cagney & Lacey, you can thank a retired grandmother living in Hernando County. And if you're happy to be living in the age of intelligent, post-Sopranos prestige TV, you can give Dorothy Swanson a hat tip for playing a small role in that, too.

National headlines called her "the housewife networks can't ignore." At the time Swanson, now 79, wasn't even a housewife, but a teacher. She also wasn't a professional TV critic, but she knew what she liked.

That narrative, however, that a supposedly soft-spoken Midwestern woman had assumed power in the television industry, with producers inviting her on set, executives calling her at home and Hollywood stars attending her modest events, proved irresistible to journalists who covered TV in the late '80s and early '90s. That fueled her rise even more.

The life and death of her organization, Viewers for Quality Television, and other stories of television superfans wielding collective power to save shows from cancellation, is the subject of the new documentary, United We Fan. It's available Dec. 4 on iTunes, Amazon, and most cable video on demand platforms.

"At this stage in my life, it's really an affirmation of those 15 years or so of advocacy," she said. "I have a group of friends here who saw the trailer and were going 'Why didn't you ever tell us you did this?' The reason is, where do you start?"

It started in 1983, when Swanson fell in love with the new series Cagney & Lacey, which stood out to her with its quality acting, writing and strong female leads, Tyne Daly as Mary Beth Lacey and Sharon Gless as Christine Cagney.

Then it was canceled, and "something snapped."

Swanson began writing letters to CBS, and through a grassroots effort that started with friends, she convinced others to do the same. The TV columnist at the Detroit Free Press picked up the story, the first of dozens of newspapers and magazines to write about Swanson in the coming years. The show's producer threw his support behind her effort.

After being deluged with hundreds of the letters, CBS put the first season of Cagney & Lacey back on in reruns, where Swanson's ongoing campaign helped it rise to No. 1 in the ratings.

When the show went back into production for a second season, TV Guide's cover said "Welcome Back, Cagney & Lacey — You want them! You've got them!" The show went on to 38 Emmy nominations and many wins.

Swanson, vindicated and feeling powerful, founded Viewers For Quality Television, an organization that for the next 15 years brought together thousands of television fans who subscribed to the monthly newsletter, voted on shows worth saving and mounted campaigns. The group saved flagging series like Quantum Leap, which legendary NBC president Warren Littlefield admits in the film moved timeslots through the efforts.

Viewers For Quality Television eventually organized a convention and awards ceremony. Swanson made taken aback stars like Julia Louis-Dreyfus stand in single file line backstage before receiving their trophies — she ran the event like an elementary school teacher.

Kelsey Grammer cried during his acceptance speech. Now-disgraced CBS executive Les Moonves admitted Swanson was a thorn in his side.

Entertainment Weekly ranked Swanson No. 82 on its annual list of the 101 most influential people in entertainment.

"The first time I saw the documentary, I was still astounded that anybody cared about this 30 years later," said Swanson, who had already thrown out most of her papers and photos from her TV advocacy days when a producer contacted her last year. "The second time I saw it, I could really appreciate what Scott Bakula and some of the other players at the time, who remember what it was we accomplished, had to say."

United We Fan also shines a light on separate fan-mounted campaigns to save shows such as Chuck, Person of Interest and Jericho. Such campaigns are commonplace today. But the documentary starts even before Swanson's time. It goes back to Bjo Trimble, the woman without whose letters we might not have had more than one season of the original Star Trek, a franchise that is still very much alive 50 years later.

And it draws a line between the work of Viewers for Quality Television, which threw its weight behind thoughtful, intelligent shows in an era when that was far from the norm, and the "peak TV" we have today.

The nonprofit Viewers for Quality Television died off in 2001, which was fine, because Swanson had achieved her mission of teaching fans that they could empower themselves. She moved to Spring Hill right after that, and put her time into working with cat rescues, rarely looking back to the era she rubbed elbows with the famous and powerful, until now.

Social media has taken the place of letter writing, and there are many new avenues for shows with a cult following to take and survive until they get a proper ending. When fans sent the network Mars bars in support of Veronica Mars, the creator launched a Kickstarter to get a movie made. After fans sent bananas in support of Arrested Development, Netflix brought it back to life.

Swanson still watches TV, but now she's mostly a "cable news junkie. She has faithfully followed House of Cards, and she loved The Americans, a show that was always critically acclaimed, and never had good ratings. Years ago, it was the kind Swanson would have campaigned to save. Nowadays the network was happy to let the series have a finale. There is value in having a complete show viewers can discover years later, streaming on demand.

Contact Christopher Spata at cspata@tampabay.com. Follow @SpataTimes on Twitter.