Why has Madonna lasted so long? Even now, in her decline, she is more interesting than the various young blonde updates that were supposed to replace her.

Yvan, a French Canadian writer, looks into his crystal ball at Madonna’s past and discovers her magic charm. Madonna, you see, is an Artist, with a capital A.

Trained and molded by the New York art scene during her scruffy bar-band days, Madonna made herself into an art object, a fiction, a canny, post-Warhol Marilyn Monroe.

“Britney Spears,” lamented Interview magazine editor Ingrid Sischy, “looks like a mall rat when she’s not doing one of her videos.” This prompted culture gadfly Camille Paglia to observe: “It shows the gigantic gap between Britney and Madonna, who has always had a superb instinct for the still photograph. Madonna’s career is much more than dance music and sensational videos. It’s also a phenomenal series of still images.”

Such as the one at left, from Sex, Madonna’s first and mercifully not-for-children foray into publishing. The ass, so the legend goes, belonged to none other than Joey Stefano, whom Nightcharm calls the greatest bottom that ever lived. (UPDATE: Our readers contend the lovely bubble butt belongs to Tony Ward, a Madonna boytoy who appeared in her videos. See comments below.)

Madonna’s enduring hold on the top spot of music charts, as well as the culture’s imagination, can be traced back to her early years kicking around the art world of New York’s East Village in the 1980’s. It was there she learned the lessons of the postmodern canon: revival, appropriation and rediscovery.

Not yet famous and in the midst of a brief affair with the painter Jean Michel Basquiat, Madonna befriended the gay graffiti artist Keith Haring, who was to have a profound impact on her later career.

“We were two odd birds,” Madonna would later reflect. “I’ve always responded to Keith’s art from the very beginning. There was a lot of innocence and joy that was coupled with a brutal awareness of the world.”

Though seemingly childlike, Haring’s graphic style was the product of art school training and a neo-Pop sensibility. At left, Haring wrestles Michelangelo’s David, and, we hope, cops a feel as well. Behind him, a typical Haring mural.

“There’s a lot of irony in Keith’s work,” noted the singer. “Just as there’s a lot in mine”

As two young kids hanging around a fiercely competitive New York art scene dominated by 30 and 40-year olds, Madonna and Haring had a lot in common. For one thing, they were both the same age. Born in 1958, they went through their teens during the sexual revolution of the early 70’s. Sexuality, in its many forms, remained a strong source of inspiration for them both.

Haring, who made no secret of his homosexuality, willingly told interviewers, “It was always impossible to separate art and life for me, and life was inevitably dominated by sexuality. It’s probably the driving force behind all my work.” At his prompting, Madonna would one day do her Sex book, now a collector’s item, which featured high-fashion and often exquisite nudes of the singer by Conde Nast photographer Steven Meisel.

In several important ways, Haring paved the career path Madonna would travel. Like the singer, Haring broke the barrier between high art and street chic. His first canvases were empty billboards in New York subways, where his “radiant baby,” at right, became a common, if perplexing sight to commuters.

He was soon picked up by trendy store-front galleries in the East Village. A budding cadre of young critics noted that Haring’s work was in no way naive graffiti scribbles but a savvy merging of hip-hop culture with symbolist painting.

At first establishment art magazines resisted. Just as Madonna would be dismissed as a transitory bubble-gum princess, so the prestigious critic Robert Hughes saw Haring as merely “a disco decorator.” This in no way stemmed the artist’s success: When Haring died at 31 from complications due to AIDS, he left behind an estate in excess of four million dollars.

A characteristic of Madonna, the ability to travel between high and low culture, may have been learned from Haring. The artist preferred the club scene in Manhattan, for instance, to the pretentious dinner parties that were given in his honor, where he might leave early to meet up with friends in the frenetic, sexualized atmosphere of a dance floor.

Like Haring, Madonna could be at home in many, sometimes contradictory, worlds. The Madonna of 2006, for instance, travels with ease between the moralistic dictums of the Kabbalah and the mirrored-ball nostalgia of her disco revival album — this last, a symbol of — and perhaps a longing for — the faded sexual revolution and her edgy teenage self.

Yes, it’s getting harder to remember but “Madge” — as the British tabloids have dubbed her, partly for putting on airs in an English country manor and partly because she has become an insufferable hausfrau with babies ever in tow — was once a hot little spitfire from Michigan, who did videos where she played booth-store strippers and sang against a field of burning crosses.

Does anyone remember now that she was once threatened with arrest for simulating masturbation on a Toronto stage? Or that she did a video — Like a Prayer — that had churchmen up in arms when she kissed the feet of a plaster saint, who immediately shed tears (metaphor alert, what else comes when you’re kissed?) and came to life in the form of a very pretty, effete black boy?

Yet at the height of it all, in 1992, just as her Erotica tour was getting underway, Madonna would insist, somewhat incredibly, “Everybody probably thinks that I’m a raving nymphomaniac, that I have an insatiable sexual appetite, when the truth is I would rather read a book.”

Perhaps internal contradictions like this is why the Mexican artist Alberto Gironella, who did her portrait, called her “the last surrealist.”

Certainly here at Nightcharm, we can never overlook one other thing she had in common with Haring: a passion for mocha-brown mixed-race boyfriends: Madonna with Carlos Leon, the father of Lourdes, and Haring with his blatino boyfriend, the DJ Juan Dubose.

Also we note Madonna’s lifelong interest — and now substantial collection of Tamara de Lempicka paintings, noted for their swanky, art-deco lesbianism (at right). Lempicka, who was a sexual adventuress with both men and women, seems yet another art-world model for the singer.

Of late, Madonna has questioned her past sexual posturing, wondering if the message that she was sending was really the one she wanted to get across.

She needn’t be so worried. We got the message loud and clear. Madonna was positioning herself as an artist, a postmodern Marilyn Monroe — canny, ironic, and not about to self-destruct any time soon.