If the political satire “Thank You for Smoking” says anything, it’s that no one plays an asshole better than Aaron Eckhart. Eckhart first gained fame playing a menacing womanizer in Neil LaBute’s “In the Company of Men.” Then, he became a spine-tingling creep in “Nurse Betty” (also directed by Labute). Now, in “Thank You for Smoking,” he plays yet another unlikable character, Nick Naylor — a fast-talking tobacco lobbyist. Somehow Eckhart always manages to bring a certain charm to the slimebag characters he plays. It’s that lovable sleeze that makes “Smoking” a blast to watch.

In the film, Naylor, who acts as a spokesman for big tobacco, launches a campaign to get today’s film actors puffing away on the silver screen (a la Boggie and Bacall) after a zealous congressman (William H. Macy) tries to put a poison label on all cigarette boxes. In Naylor’s quest, he crosses paths with a slew of zany characters, but the most memorable is a Hollywood power mogul played by none other than Rob Lowe (oh, the irony).

There isn’t a moment in “Smoking” that lacks sarcasm (hell, just read the title). Each scene is jam-packed with wry humor and virtually every line of dialogue is a punch line. Sometimes it works ­— like the hilarious scene where a video clip of killer whales eating seal pups plays in the lobby of a Hollywood talent agency — but most of the times the film tries too hard to be clever.

First-time director Jason Reitman (son of Ivan) adapted “Smoking” from the eponymous novel written by famed conservative satirist Christopher Buckley, (son of William F.). Obviously, the film was rife with potential, but unfortunately, it is too self-aware. It is apparent Reitman is influenced by Labute’s sense of dark humor and dense irony, but unlike Labute’s films, “Smoking” just doesn’t know when to quit trying to get a laugh.

“Smoking” poses as an expose of the tobacco industry, but if you want a scathing look at the cigarette industry check out Michael Mann’s “The Insider.” There are few revelations in the film: Naylor is a cutthroat businessman who vows to buy his beloved son his first pack of cigs when he turns 18 — tobacco lobbyists are unscrupulous, who knew? The story is also a bit dated: Buckley did pen the novel back in 1994. That said, most of the time, the performances make up for the lackluster writing. “Thank You for Smoking” sports a cast of the indie world’s elite: You’ve got Sam Elliot as a cancer-stricken Marlboro man, Robert Duvall as a tobacco CEO and Katie Holmes as an ambitious reporter (the one poorly casted actor in the whole film).

But the most interesting characters are the M.O.D. (Merchants of Death) squad. They are a triumvirate of lobbyists from big tobacco (Naylor, who else?), big ammunition (David Koechner from “Anchorman”) and big booze (Maria Bello). The squad, who lunch once a week to gripe about the travails of shilling their respective hazardous products in an increasingly health-conscious society, have the cleverest scenes in the movie.

Not to be outdone, Eckhart’s charisma never wavers. As Naylor, he is always charming, always entertaining, whether unapologetically pushing cancer sticks or playing dad. Being the asshole might seem like a thankless job, but in Eckhart’s case, it pays off.