Spoiler alert! Includes details about the first episode of HBO’s “The Regime."

She converses with her dad’s corpse, touts the therapeutic qualities of potato steam and is carried around in a plastic case by guys in hazmat suits.

Yet the most crackpot thing about Elena Vernham (Kate Winslet) might be her singing. In the series premiere of HBO's “The Regime” (Sundays, 9 EST/PST and streaming on Max), the erratic chancellor hosts a state dinner for dignitaries of her fascist, unnamed European country. At one point, she goes onstage and serenades the crowd with Chicago’s 1976 hit “If You Leave Me Now”: cringingly off-key, but delivered with full-throated gusto.

“It’s such a great metaphor,” Winslet says. “I thought that song choice was very much to do with her trying to express her gratitude for her loyal followers. It's a fantastic play on the world of ‘likes,’ and how she’s a leader by social media more than anything.”

Review:Kate Winslet's 'The Regime' is dictators gone wild. Sometimes it's funny.

Why Chicago's 'If You Leave Me Now' soundtracks 'The Regime'

Will Tracy (“Succession”) created the six-episode HBO dramedy, which blends outrageous political satire with a toxic romance between Elena and Herbert Zubak (Matthias Schoenaerts), a brutish soldier who becomes her new bodyguard. “If You Leave Me Now” was written into the script’s very first draft, so Tracy was relieved when Chicago frontman Peter Cetera later signed off on it.

“I was trying to think of an American song that might’ve hit the airwaves in Europe when she was a kid: something seemingly innocuous and maudlin and soft rock,” Tracy says. “But I always felt there’s something in that rising hook in the melody; there’s a sadness contained in a lot of those seemingly vacuous radio ballads. So it seemed like the right song to mine for a ridiculous moment at the top of the show,” but one that also becomes “strangely poignant” by the series’ end.

Winslet prerecorded the audio track at London’s famed Abbey Road Studios. (“It was an unbelievable moment for me,” she says. “I’m recording on the same stage as the Beatles did!”) Reading the script, she figured Elena was a strong singer. But after the first take, “Regime” director Stephen Frears walked into the recording booth looking puzzled.

“He said, ‘Sing it badly,’” Winslet recalls. “It was a brilliant piece of direction, because it let the audience know that you’re supposed to laugh. ‘Welcome to this delusional woman’s world.’ So that was my biggest note: Do it worse!”

Kate Winslet clears the air on her alleged 'pop career'

“Regime” is hardly Winslet’s first time singing onscreen. The Oscar winner has a lovely voice, which she lent to many of her films in the 1990s, including “Heavenly Creatures,” “Sense and Sensibility” and “Holy Smoke!”

“I do enjoy singing,” Winslet says. “I sing around the house a lot. My husband (Edward Abel Smith) probably enjoys it more than I actually think he should. I’m not really that good.”

She also recorded a theme song, “What If,” for 2001’s animated “Christmas Carol: The Movie.” Winslet initially agreed to do a version as a placeholder, assuming the film's producers would find another artist to record the ballad.

“They all seemed to really like it, and then they wanted to release it as a single,” Winslet recalls. “I was like, ‘Oh, my God, this is bizarre.’ I said ‘OK, that's fine, but all the proceeds absolutely have to go to children's charities.’ But that was never really made clear, so it totally looked like I was trying to launch a pop career."

British newspaper The Guardian even published an article about the actress’ alleged pivot to music. But she wants to set the record straight: “I was never attempting to embark on a singing career! I like acting too much.”

Winslet teases a 'terribly inappropriate' Christmas song

Winslet sings twice more in “Regime." In one episode, she leads a pitchy “Happy Birthday to You” at a party for her late dad.

Later, she performs a full-blown “Santa Baby” production number as part of a tone-deaf holiday greeting for her nation’s disgruntled citizens. "It's a lurid combination of something that feels very infantile and very sexual," Tracy says of the song, which has been teased in the series' trailers. Winslet says she and the show’s costume designer, Consolata Boyle, spent hours on Google researching “trashy Santa elf costumes” for the scene.

“I was like, ‘Let’s just go for it,’” Winslet recalls. “It was just so funny how terribly inappropriate the whole thing was: those frilly little under-knicker things and that stupid little hat. She’s so deluded! That’s her Christmas address to her people. There are things built into this show that are just so unbelievably absurd."