It is one of the least-known ironies of current America: When it was time for Gabourey “Gabby” Sidibe’s “Late Show With David Letterman” close-up to plug her starring role in the wallopingly powerful film“Precious,” she was, quite suitably and predictably, treated by the host onstage as the promising but hitherto unknown star of one of the great films of 2009.

PRECIOUS

Four stars (out of four)

Rated: R

Gabourey Sidibe, Mo’Nique, Paula Patton, Mariah Carey and Lenny Kravitz in Lee Daniels’ much-praised adaptation of Sapphire’s novel “Push,” about an overweight, pregnant teenager in Harlem trying to emerge from a relentlessly horrific home environment.

And yet if Sidibe (pronounced SID-uh-beh) had come into the Ed Sullivan Theater as an audience member that night, the richly talented but enormously overweight actress would likely have been diverted at the door as far as possible from all the front-row orchestra seats that are likely to get on camera during an audience pan shot – especially if there were some segment that night that called for Letterman to wander out into the audience.

The “visible rows” on the show are generally reserved for those audience members they want glimpsed on camera—acceptably ordinary middle Americans, decently dressed and coiffed, pleasantly fragrant rather than pungently aromatic.

As an audience member, she would have been in the back, maybe even the back of the balcony.

Invisible. It is that very disparity between human reality, in all its rudeness and even nightmarish horror and social invisibility, and the friendly, homogenized Girl Scout cookie version of it that the Entertainment Industrial Complex prefers that makes Lee Daniels’ film one of the most powerful new films you’ll see in 2009.

And that disparity is one of the things this film is about. That’s why Mariah Carey is in it wearing no makeup (she figures prominently in the finale, the film’s most powerful scene); that’s why Lenny Kravitz is in it —playing a nurse’s aide.

This is a movie on a mission —to give you the America you almost never see in a commercial movie anymore. It is a fact of post-Oprah, post-Obama America that, incredible as it may seem, there is a sizable audience that hungers for the reality this movie wants to give it, as horrendous as that reality is.

And it is gruesome.

The movie is based on the book “Push” by the 59-year-old novelist and poet Sapphire (her real name is Ramona Lofton). It is about hugely overweight 16-year-old Clareece “Precious” Jones, pregnant for the second time after she has been raped by her father (her first child is a girl with Down syndrome) and living with a mother (comedian Mo’Nique), whose verbal and physical abuse is unrelenting.

“Don’t nobody want you and don’t nobody need you” is her mother’s life message to Precious.

What middle-class Americans routinely toss off as “self-esteem” is non-existent for her. She dreams of being on the cover of a magazine. When she looks in the mirror, the image she wants to see looks more like Drew Barrymore. Education, and its tests, bring her nothing but fear that they’ll reveal her to be a spot of “big black grease to be wiped away.”

When her pregnancy is discovered, she is taken out of conventional high school (where she seems to have considerable math aptitude) and forced, by a teacher who won’t take no for an answer, into an “each one, teach one” alternative school.

And there she meets yet another social miracle—a beautiful teacher (Paula Patton) who, similarly, refuses to allow Precious another minute of Zero Degree Self-Esteem. She forces her and the rest of the girls in her class to write daily in a journal.

They become a true class— a small coherent society.

While her mother only wants her around for the welfare check she provides, the welfare social worker (Mariah Carey) is just as adamant about not allowing Precious to be “wiped away.”

Precious is, then, somewhat incredibly surrounded by people who insist on giving evidence that the “system” can work.

It’s all too easy to be cynical here and say that the whole movie is like Mariah Carey without makeup—a beautiful and reassuring “extreme makeover” tale to uplift rather than a truth for its own sake, much less art’s sake.

But the movie simply refuses to play that way. In its final scene, with Mo’Nique stark and harrowing as she explains herself to Precious and her social worker, the movie refuses to airbrush the horror away. It’s too good and too smart for that.

Not least of the small miracles of “Precious” is that its provenance couldn’t possibly have been more unexpected for film cognoscenti of all shapes and sizes (pro and nonpro).

Who among them would have expected that Oprah Winfrey and Tyler Perry would be the ones to team up in the background to get one of the year’s great movies going in the first place?Who among them would have expected that its director would be Lee Daniels, previously known for a truly wretched hired assassin movie called “Shadowboxer” starring Cuba Gooding Jr. and Helen Mirren?

There is a makeover happening in this movie, which is why it has the massive emotional power it does. But it’s never cheap.

With total honesty and integrity, it rewards its audience with huge emotions for being the kind of audience that it wants itself to be.

An exceptional moment in this movie year.