How did television become the repository for characters afflicted with Munchausen syndrome by proxy?

Talk about trending! That strange psychological disorder — in which someone seeks attention by exaggerating or making up a child’s illness — reared its ugly head in two of this season’s Emmy-nominated productions (HBO’s “Sharp Objects” and Hulu’s “The Act”) and returns this fall in Netflix’s “The Politician.” The first series, based on Gillian Flynn’s novel of the same name, was fictitious, the second was based on a true-crime article first published in BuzzFeed, and the third borrows from both.

With echoes of the grisly dynamic between Jane and Blanche, the twisted sisters Bette Davis and Joan Crawford played in “What Ever Happened to Baby Jane?,” the Munchausen story has proved a boon to middle-aged actresses unafraid to walk a tightrope between melodrama and camp. Patricia Clarkson, who played the toxic mother of “Sharp Objects,” and Patricia Arquette, the domineering mom of “The Act,” are competing for an Emmy Sunday night for their supporting roles. In the wings is Jessica Lange, playing another one of Ryan Murphy’s lunatics in “The Politician,” which premieres Sept. 27.

Not all three keep their balance on that tightrope.

Playing several Tennessee Williams heroines rolled into one (Blanche DuBois, Amanda Wingfield, Mrs. Venable), Clarkson steals “Sharp Objects” from star Amy Adams with her chilling portrayal of a mother who killed one daughter and hopes to finish off another by keeping the girl indoors, spoon-feeding her antifreeze and inducing her to vomit. It takes Adora’s eldest daughter, a journalist (Adams), and a handsome detective (Chris Messina) to stop her.

Arquette’s Dee Dee Blanchard, meanwhile, is running a scam, telling her teenage daughter, Gypsy Rose (Joey King), that she’s gravely ill with cancer while accepting donations from strangers who’ve heard of the girl’s plight. Eventually, Gypsy discovers she’s not sick at all and struggles to achieve some measure of independence by (spoiler alert) asking her boyfriend to kill her mother.

Arquette, who’s up for another Emmy on Sunday as Tilly Mitchell in “Escape at Dannemora,” does a deep dive into Dee Dee, transforming herself yet again into another frighteningly real, fractured woman who’s lost all touch with reality.

Both Dee Dee and Adora are a far cry from Lange’s campy pastiche as Dusty Jackson, a white-trash mama who thinks she’s fooling the world about her daughter’s illness in “The Politician.” Since this is a Ryan Murphy series, everything is overdone, and Lange, who enjoyed a comeback with Murphy’s “American Horror Story,” doesn’t let her employer down. She cooks bologna cups for dinner, shrieks like a banshee when Infinity (Zoey Deutch) is hospitalized and practically breathes fire into the face of Payton Hobart (Ben Platt), who’s running for office at the high school he and Infinity attend. Invalid Infinity (see the irony in that?) is his running mate.

Clarkson won a Golden Globe for “Sharp Objects,” where she wasn’t competing with Arquette, who won in the lead category for “Dannemora.” It will be interesting — and revealing — to see which crazy mama the Television Academy prefers Sunday night, or whether they will cancel each other out. Lange, an Emmy favorite, will be in the running for the 2020 awards, when she’ll likely be up against her old Oscar nemesis, Meryl Streep, the crazy mama on “Big Little Lies.” In that series, Munchausen syndrome by proxy wasn’t her character’s problem: Determined to declare her daughter-in-law (Nicole Kidman) an unfit mother, she was just plain crazy.

Murphy’s “Feud” showed what happened to Bette Davis and Joan Crawford after “Baby Jane” became a hit: It seems that once an actress goes off the rails, she rarely comes back. With any luck, times have changed — and Hollywood will offer its veteran actresses better roles than the crazy mothers they’ve already played.