St. Louis ? It would be the fashion feat of the decade.

Maybe the feat of all time — at least in the history of facial hair.

The task? To repopularize a 1970s relic that suffered the same fate as the perm, the turtle neck and disco. Not to mention tie-dye, pet rocks and Quaaludes.

And what more suitable place for a rebirth of the “lip sweater” than St. Louis? Home to the Gateway Arch. Also known as the “world’s largest mustache.”

Of course, the crusade began the way many great ideas do: with a handful of guys and food. Three years ago, Aaron Perlut was sitting in the corporate lunchroom of Fleishman-Hillard, a public relations firm, with a half-dozen colleagues.

Out of that casual conversation came a mission. They would resurrect the mustache.

“It was an utterly random conversation,” recalled Perlut, who sports a fine Arch-inspired ‘stache.

Today, the movement Perlut and company created — the American Mustache Institute — is a well-waxed operation. Just a few weeks ago, Jay Leno mentioned it in his opening monologue. And the topic even came up at a press conference with U.S. Attorney General Eric Holder, who proudly displays his own lip sweater.

The experiment helped lead Perlut and two other Fleishman employees, Dan Callahan and Brian Cross, to break away and create their own firm, called Elasticity.

The company’s message is that in today’s information age, the best public relations strategy is one of flexibility, using traditional media, social networks and digital marketing. An example they trot out to prospective clients: their work in relentlessly hyping the American Mustache Institute.

There’s also a charitable element to the cause, raising money for a good cause.

Goulet connection

And it all comes back to mustaches — in particular, to the mustache of the late Robert Goulet.

The Web site — americanmustacheinstitute.org — declares the goal of creating “a climate of acceptance, understanding, flavor saving, and upper lip warmth for all mustached Americans alike.”

And recently, it released a “study” claiming that mustached men earn 4.3 percent more than the clean-shaven — or those plagued by what the institute calls “bare-upper-lip disorder.”

This much is real, though: “‘Stache Bash,” an annual celebration of “mustacheology.”

The first ‘Stache Bash in 2007 had about 50 people. Last year, the bash grew to more than 800. And this year, the group rented out the Roberts Orpheum Theater. They’ve even hired the mustachioed John Oates, of Hall and Oates fame, to perform.

The event raises money for St. Louis Challenger Baseball, a league for children and adults with disabilities. Buck Smith, the league organizer, said proceeds from ‘Stache Bash are no joke — they amounted to $15,000 last year.

At ‘Stache Bash, the institute announces the winner of the prestigious “Robert Goulet Mustached American of the Year” award.

Why Robert Goulet? The group chose him as its standard-bearer not only because of his famous facial hair, but also his renowned sense of humor. They even got the OK from his widow.

Go-to guys

Over the last couple of years, the American Mustache Institute has become the enthusiastic and willing source of observations on facial hair for media outlets. It has graced the pages of the New York Post, USA Today and the Dallas Morning News, among others.

In 2007, ESPN producer Gabriel Goodwin wanted to do a story about sports and mustaches. An Internet search brought him to the American Mustache Institute.

Perlut appeared on air as “Dr. Aaron Perlut” (as in doctor of “nuclear mustacheology”), complete with white lab coat and a stethoscope. The doctor touted research showing that a resurgence in then-New York Yankees slugger Jason Giambi’s batting average was due to his new mustache.

ESPN anchorwoman Dana Jacobson asked, “How much credit do you give that strong mustache for his play?”

Perlut replied: “I would give it at least 75 percent of the credit. Our studies have shown that the mustache can increase manly-hood by 68 percent.”