Olive Kitteridge is a critic's conundrum.

Some viewers will find it a hopelessly tedious slog through 25 years in the life of a crusty retired schoolteacher in coastal Maine.

Others will hail it as a remarkable artistic accomplishment, illuminated by two of the finest performances you will see in any medium this year: Frances McDormand as the stoic, deeply unhappy Olive and Richard Jenkins as her sunny Jack Sprat of a husband.

Based on Elizabeth Strout's prize-winning story collection, Olive Kitteridge (9 p.m. Sunday on HBO) lays bare the thousand ways in which we disappoint one another and proves that even frozen hearts can ache.

It's also a reminder of how powerful a TV movie can be. The poor, maligned genre once ruled over prime time, the way NFL telecasts do today.

In the late '60s, the networks divvied up the week, each devoting at least two nights to movies. Over the years, the format provided powerful dramas like Brian's Song with James Caan and Billy Dee Williams, My Name is Bill W with James Woods and James Garner, and The Burning Bed with Farrah Fawcett.

The appetite for script material was so voracious that often the networks were racing to get the same torn-from-the-headlines treatment on the air first. Case in point: Amy Fisher, the "Long Island Lolita." (Her sordid tabloid scandal was a big deal. You can look it up.)

Then, with startling finality, the TV movie - and its burly brother, the mini-series - became an endangered format on broadcast.

In 1989, Murderers Among Us: The Simon Wiesenthal Story on HBO became the first cable project to get nominated for an Emmy as outstanding drama/comedy special (the category that the made-for-television movies fell in at the time).

By 1996, the networks were shut out of the category by cable, a dominance that became the norm. The last network movie even to get nominated was A Raisin in the Sun in 2008, and it had been eight seasons since that had last happened.

What caused the great migration to cable?

In part, it was the volatility of the format. TV movies were always a crapshoot, ratings-wise.

"One week, you might have a hot topic, the next, you might put on something that didn't resonate," says Arturo Interian, vice president of movies at Lifetime. "The networks went with the surer bet." That means series, which tend to draw consistent numbers week after week.

In part, it was the nature of the venue that led the nets to abandon the genre. They had to recoup production costs with a single airing. It simply wasn't viable to repeat the movie of the week.

Their wired competitors didn't have that restriction. "In cable, you can run a movie 12 times and get different viewers every time," says Michelle Vicary, executive vice president of programming and network publicity for Crown Media, which runs the Hallmark Channel.

Cable channels, whether ad-supported or pay, can also survive comfortably with much lower ratings. So they became the logical environment for made-for-TV movies. Now, cable outlets are the ones banging heads over the same concepts, like the dueling movies about the "romance" of Prince William and Kate Middleton.

It has become a thriving industry for some channels. Syfy will show 15 original movies in 2015 (including Lavalantula); Hallmark will show 55!

Everyone has gotten into the act, from History (Houdini) to National Geographic (Killing Lincoln) to Discovery (Klondike).

"When we started out, it was all women-in-jeopardy," says Lifetime's Interian. "But as the landscape has gotten more competitive, we've really had to up our game. The casts and the production values have gotten better and better."

As the prestige and the ratings have grown (even Sharknado 2 drew 3.9 million viewers), the networks are starting to loiter around the edifice they once abandoned.

Nearly 19 million people tuned in to NBC's live revival of The Sound of Music in December, a success the network hopes to duplicate next month with Peter Pan.

The networks are ambitiously experimenting with expanding the format, working in longer multihour formats like Extant, Gracepoint, Rosemary's Baby, and M. Night Shyamalan's coming Wayward Pines.

It's a strategy that has already proved popular on cable (True Detective) and streaming services (Netflix's Orange is the New Black).

The lengthier projects are better suited to today's binge-watching, video-on-demand climate. But no one has settled on a name for them.

"We don't call them miniseries anymore," says CBS vice president Stacy Mandelberg. "We now call them limited series or event programming."

It's causing a lot of confusion at the Emmy Awards, rendering the categories almost meaningless. Last year, Fargo and American Horror Show entered themselves as mini-series, although neither qualifies. And Downton Abbey, which used to run as a mini-series, has taken to identifying itself as a drama series.

Say what you will about the made-for-television movie. It never pretended to be something it wasn't.


Olive Kitteridge

9 p.m. Sunday on HBOEndText

215-854-4875 @daveondemand_tv