“Boss” 10 tonight, Starz

The politician, preparing to unleash a negative onslaught on an opponent, is startled to hear one of his own advisers object that they’re using “unsubstantiated” dirt. “I’ve got no qualms about hitting him with unsubstantiated (bleep),” the politician barks. “Unsubstantiated (bleep) is exactly what I’d like to bury him with.”

Welcome to the political underworld of “Boss,” where rules are written with bare knuckles and the losers leave in body bags. Starz’ new eight-episode drama is at once the most cynical and most captivating portrayal of American politics ever presented on television.

“Boss” stars Kelsey Grammer in a role about as far as humanly possible from the lightheartedly fussy psychiatrist he played for two more than decades on “Cheers” and “Frasier.” In “Boss,” Grammer plays Thomas Kane, a longtime Chicago mayor and political kingpin who smiles like Santa Claus in front of the voting audience but runs things backstage with the ruthlessness of an ayatollah — literally. One ward boss who runs afoul of Kane loses his ears as a reminder of who’s boss.

But Kane has finally encountered an enemy who cannot be badgered or bullied or bribed into submission: a Parkinson’s-like disease that is already giving him tremors and momentary blackouts, and soon enough will reduce him to hallucinations, dementia and death.

He gets the news, appropriately enough, in an abandoned slaughterhouse, where he meets secretly with his neurologist. In the jungle ethos of Kane’s world, the prospect of death is far less threatening than the possibility of displaying weakness to his enemies, and he keeps the news of his illness strictly to himself, even allowing his wife to think the neurologist is his mistress rather than his doctor. Not that there’s anything of romance left in the marriage.

Stony hearts and political calculation, however, are not exactly in short supply in “Boss.” This is a show about how political sausage is made and sliced up, and the spectacle is every bit as bloody as the back room of a butcher shop. The so-called reform candidate Kane is backing for governor (Jeff Hephner, “The O.C.”) is practically indistinguishable from the corrupt old warhorse (Francis Guinan, “The Last Airbender”) he’s trying to unseat.

“Boss” sometimes explodes into unexpected violence or sexual kink. More often, though, it’s deeply thoughtful, filled with literary and historical allusions that would have caused an epidemic of incapacitating strokes among television executives back in the bad old three-channel days.

Some of the subjects might have been surprised, too. Doubtless the socialist rabble-rouser Upton Sinclair would have been amazed to find himself transported into the living rooms of Starz’ upscale audience to proclaim, “Life, with all its cares and terrors, is not such a great thing after all for a laborer or a hog.” And after watching “Boss,” he might have added: “But it’s pretty damn good for a politician.”