Whither the mustache? Not so long ago, it was a sign of macho virility as embodied by Tom Selleck. But in recent decades, it has been viewed as, in the blunt words of the independent and mustachioed filmmaker Jay Della Valle, “skeevy.”

Right now, however, the mustache is having a moment. Mr. Della Valle’s new documentary, “The Glorius Mustache Challenge,” in which he chronicles the experiences of under-30 men growing mustaches, will make its premiere Thursday, followed by a celebratory “mustache soiree.” Just a few blocks away on the same night, the charity Mustaches for Kids (M4K) will hold its annual competition to determine who will be crowned Mustache King of New York. Proceeds go to the Children’s Hospital of New Orleans.

Meanwhile, in the world outside of downtown Manhattan, one of the television season’s most popular new sitcoms, “My Name Is Earl,” stars a mustachioed Jason Lee as a likable lay about who wins the lottery. Whether it’s the mustache or the writing, the show is moving up in the world: NBC announced that in January, “Earl” will move to the prominent Thursday-night block of comedies, where the network hopes the anti-hero will find an even larger audience.

With a mustache making appearances on the faces of trendsetters and primetime TV stars, is the look ready to break out of the “skeevy” enclave and make a serious play for the mainstream?

“A man without a mustache is no longer a man,” a woman in Guy de Maupassant’s 1883 epistolary short story “The Mustache” lamented. “The mustache is the spice.” Throughout most of the 20th century, the mustache was indeed the spice. Charlie Chaplin, Groucho Marx, Errol Flynn, and Clark Gable made the style suave in the earliest decades of the movies. Later, Burt Reynolds had one in the 1977 film “Smokey and the Bandit,” and Mr. Selleck sported a thick brush in the 1980-88 television show “Magnum, P.I.” (It also became a mark of villainy, thanks in part to the mustache-twirling cartoon character Snidely Whiplash – not to mention dictators from Hitler to Hussein). But its prominence didn’t last.

The executive editor of men.style.com, Tyler Thoreson, says that today, “Pop culture has been utterly de-mustachified.” No major movie stars have mustaches anymore, nor do teen heartthrobs or anchormen. As Mr. Della Valle sees it, the mustache is now generally thought of as the realm of “homosexuals, white trash, child molesters, cops, and uncles.” In perhaps the clearest sign that the ‘stache had fallen out of mainstream favor, the creators of Brawny paper towels “shaved” their iconic Brawny Man in 2003. The new image, a company executive, Michael Burandt, said at the time, “Signals to shoppers that these towels are completely updated and have moved into the new millennium.” Mustaches, in other words, are so last century.

Recently, however, the style has made urban inroads by way of hipster icons such as photographer Terry Richardson, American Apparel founder Dov Charney, and Gogol Bordello lead singer Eugene Hutz.

Mitch Goldman, one of the organizers of the New York division of Mustaches for Kids, sees signs of a return. “This is a banner year. We don’t know what happened, but there are somewhere between 40 and 50 people participating in New York City.” Most years, he said, the event draws about 25 competitors. The success of the organization in cities like New York, San Francisco, and Madison, Wis., suggests a certain retro-chic currency.

Mr. Thoreson says that for a real breakout, “A poster boy needs to emerge. It needs a representative.” When a serious mainstream star embraces the style unironically, he said, the mustache will have arrived. It’s the law of hipness: There are only so many ways to arrange fabric, makeup, and facial hair, so recycling is inevitable. “It happened with big collars, it happened with bell-bottoms,” he says.

If the ranks of 21st-century male mustache devotees are growing slowly, there are even fewer women out there who have a taste for its particular spice.

Blogger Jason Mulgrew, who was listed as one of People magazine’s 2005 list of “hottest bachelors,” sports a mustache he grew as part of Mr. Della Valle’s “mustache challenge.” He said it’s a liability when it comes to women, but then, “Women don’t respond well to me, with or without the mustache.” He had a beard when his photograph was taken for People, and he’s not sure they would have accepted a mustachioed bachelor.

Mr. Goldman says the fear of female response is the biggest hurdle to gathering M4K participants: “The most common hesitation is that ‘my girlfriend or wife would hate it.'”

Women embraced Tom Selleck, however, and they’ll likely embrace the next great mustache-wearing heartthrob. Soon, perhaps, they’ll understand Maupassant’s letter-writer’s insistence that “there is no love without a mustache.”

Mr. Thoreson, for one, thinks the last decades’ lack of upper-lip hair has “cleared the way for a new generation. “All that style-watchers are waiting for now, he said, is a major mustache moment courtesy of a bona fide tastemaker. “Someone like Tom Ford when he comes back, every model in his new collection is going to be wearing a full-on soup strainer,” he speculated. “It’s going to take guys walking down the runway, guys in full-on ‘Magnum’ mustaches. … We’re just waiting.”