Go ahead. Try it. It's 2 a.m. the day before the big pageant and only a few technicians are here in cavernous Convention Hall. The footlights are still on and it's so quiet you can almost hear the drone of the ocean beating against the boardwalk. Get on stage and do it. Walk the runway, that 135-ft. plywood sidewalk to cotton candy heaven. There you go . . .

If you walk that runway, even as Mr. or Ms. Nobody in the dead of night, it has to hit you. What do they feel like on that first Saturday after Labor Day, posing, performing, smiling? What goes through their minds?

"Will I fall? Is my elastic hitching up? Will my smile freeze on my face forever?"

Don't worry. Only seven cameras, a live audience of 23,000, and a television audience that hovers near 100 million are following your every step.

You know what some of them must be thinking: "What a looker." Or, "She doesn't know it but she's nothing but a sex object." Or, "When I grow up, maybe I can be -- dare I say it? -- Miss America."

It's that time again, time to pick the first Queen of the Reagan years.Somehow the Miss America pageant seems more appropiate now -- the colossal frosted Mini-Wheats production numbers, the contestants' numerous denunciations of ERA and abortion.

When the pageant directors fired Bert Parks last year because they wanted someone more "contemporary," they considered John Davidson and then settled on ex-TV Tarzan Ron Ely. Hunks.

But think of it, who would have been more perfect for the 1981 role than the leader of the Free World himself? President Ronald Reagan, in his tux, smiling, congratulating you, handing you the roses, crowning you, fulfilling your biggest dream.

Maybe Miss Maryland, Robin Harmon, has the biggest dream of all. If she wins, not only will she be the pride of Hagerstown, Md., she will become a historical figure, another "first," like Jackie Robinson and Thurgood Marshall. She would be the first black Miss America.

Harmon enters Saturday's contest without having won any of the preliminary competitions, a severe disadvantage for making the finals. Still, she hopes for the best. "I'm very realistic," she says. "I know my chances are only as good as the other 49 girls, so I won't break into a sweat if I don't make the top 10; besides, I'm not sure if there will ever be a black winner. So I have to be prepared for that. But I know one thing: If I do win, I'll faint. I'll probably cry a river."

Before the pageant, Harmon will pass up dinner to keep her stomach flat and will go through a kind of pre-game ritual.

"I have this horseshoe, a real horseshoe," she says. "It used to be hanging over my door but it fell off and hit me on the head so now I carry it around with me. Also, I always say a little prayer. Nothing like 'Oh dear Jesus, let me win,' but just something, you know, so that I'll do my best."

As for pageant week, Harmon said she expected something a little different. "It's not what I thought it would be," she says. "When you hear about showgirls and casinos and hotels you think of Las Vegas. But when I got here it wasn't that at all. It's just Atlantic City."

For years and years, anyone who knew Atlantic City would tell you the same thing. Never mind the boardwalk, never mind Miss America, it's a sleazoid.

But all that's changed. Now Atlantic City is a sleazoid place with casinos.

Pageant officials, however, have done their best to play down the new high-rollers aspect of Atlantic City. In this of all cities, of all states, purity is the commodity of the day.

Wink Martindale, the host of "Tic Tac Dough," stands in the gigantic parking garage in Convention Hall and ponders the qualities of his ideal Miss America. "I'm looking for a girl who is self-assured and poised," says Martindale. His word is golden. He is a judge this year, a barrister of Americana.

Foster Brooks, a judge who is most famous for his inebriated hiccupping on countless Dean Martin roasts, is asked what he's looking for during the swimsuit competition.

"I'm 69 years old and you can imagine what I look for when I watch those girls," says the white-bearded Brooks. "I look for someone who makes me gulp a few times. And who makes my wife say, 'You liked that one, didn't you?' "

Jody Barry's pageant days are far from over. Twenty-five years ago she was a multi-crown winner from Austin, Tex.: Miss Portable Appliance, Miss Firecracker, Miss Bergstrom Air Force Base, Miss Associated Service Station.

There are slight wrinkles around Barry's eyes and lips, her hair is more sculpted than shaped, but make no mistake about it: She, too, was once a star, if only for smaller stages.

Now, Barry's two daughters, Candyce, 22, and Kapryce, 20, have been local and state pageant contestants and they have joined their mother on a 27-hour bus ride from Wichita to Atlantic City so they could cheer on this year's Miss Kansas, Dawn Holmstrom.

At afternoon rehearsals, Jody Barry sits along the runway watching Miss Ohio, Julianna Zilba, belt out "Up the Ladder to the Roof," and she is smiling a very proud smile.

When the singing stops, Barry says, "You know, someone once told me that the pageant is the world's largest finishing school for girls."

Candyce Barry was second runner-up in this year's Miss Kansas competition and though she says she has come to "stand by the queen," she looks up at the stage and wonders what could have been.

"Sure, I'd love to be there," she says. Quickly, she remembers her sense of propriety and adds, "but I feel Kansas chose an excellent representative."

Kapryce Barry has lighter hair than her older sister but the same aquiline nose and gently arching cheekbones. She is quick, though, to point out her major flaw. As she smiles, you see it, bright as noon: the strings and wires across the teeth.

The obvious question: How could she have been crowned Miss Wichita 1980 with braces on her teeth?

"They went on after the judge at the state pageant told me I had a crooked tooth," she says. "I have to improve myself."

Kapryce Barry wants to win. Hence, the tin.

The week goes by quickly and though no one is eliminated officially, you can feel it happening. The field narrows. The predictions start coming in and you don't need a weatherman to know which way the wind blows.

Even before she won her talent preliminary, Miss Texas, Sheri Ryman, had POTENTIAL WINNER radiating from her like neon.

Watch her Saturday when she does her gymnastic routine to music from "Close Encounters of the Third Kind." It's a cornball routine if there ever was one, but somehow Ryman transcends her own act. She even ever-so-slightly hints at that most forbidden quality: irony. Not a lot, but just enough.

Ryman talks about marrying a "faithful Christian" with "crystal-blue eyes" and has a re'sume' loaded with entries like Noon Optimist Queen and May Fete Duchess.

Earlier in the week, Dr. George Miller, a Northern Illinois University statistics professor who has picked the last two winners correctly using a computer, tabbed Miss Texas for 1981.

Smart computer. The pageant's executive director, Albert Marks Jr., is in a tiff over the prediction. But something has to be said for any kind of technology that can interpret hazy Miss America qualities like radiance and congeniality through its transistors.

For her part, Ryman is skeptical. "The computer isn't doing the judging. It just coughed up my name. What can I say?"

Say this: Miss Texas -- Potential Winner.

For the theoretically inclined, the pageant people took their own poll of this year's contestants. Not to pick a winner, but to paint a statistical picture of the average contestant:

She is 21 years old, 5 feet 6 1/2 inches, 114 pounds, has brown hair, one brown eye and one blue eye. Her favorite hobbies are cooking and baking and she loves to swim and ski. Her best talent is her singing.

There she is, Miss Composite America 1981.