Movie actresses know that growing old can be a career killer, as detrimental as forgetting your lines or appearing in a Pauly Shore film. In television, however, serious actresses can’t age fast enough.

Female roles have become juicier in recent years, primarily on cable, but only for women of a certain age. Consider this year’s slate of Emmy nominees for best actress in a drama: Sally Field, 62; Holly Hunter, 50; Glenn Close, 62; Mariska Hargitay, 45, and Kyra Sedgwick, 43.

The single exception on the list is Elisabeth Moss, the ambitious, naive Peggy Olson in “Mad Men,” which recently returned for its third season. If Moss, who is 27, were to win, she would be the youngest winner in the category’s history.

“It’s kind of unusual to find a part like this for a woman my age that’s complex, real and complicated,” said Moss, who was born the year Field was frolicking on the beach as Gidget. “She’s not an easy person to figure out, and while that’s more and more prevalent in TV for women, it’s not for younger people.”

What makes Moss’ achievement even more impressive is that she’s inhabiting a character who deals with crises – an unwanted pregnancy, sexual discrimination at the office, the Cuban Missile Crisis, a dowdy wardrobe – without the luxury of shooting a gun or throwing a temper tantum. Instead, she became one of last season’s breakout stars by using glassy-eyed glances and awkward pauses to express anguish, frustration and triumph, all with a sugar-sweet voice that reminds you of a girl heading out for her first prom.

In the hands of other Hollywood ingenues, the character could have come across as a pouty rebel who grew up on the gritty beaches of Dawson’s Creek. But Moss excelled by pulling back, and subsequently pulling viewers in.

It’s the same technique she used to beguile “Mad Men” creator Matthew Weiner during the show’s audition period. The critical scene she read that day came from the pilot episode. In it, Olson, spankin’ new to the ad agency, hopes to warm to her boss, Don Draper (Jon Hamm), by placing a hand on his shoulder. Draper responds with a look that could freeze time. Moss’ expression of embarrassment, done without the aid of heavy blush, blew Weiner away.

“I was so emotional after I heard her,” he said. “I turned to the casting people and said, ‘Just keep bringing me more people like her.”‘

She was only the second performer to read for the series, but she never escaped Weiner’s mind. Although he had never heard of her, he sort of recognized her from TV appearances on the likes of “Picket Fences,” one of many roles that Moss took as a teenager. Most memorably, she portrayed the president’s youngest daughter on “The West Wing.”

All of this gave her experience and maturity that’s rare for a thespian in her mid-20s.

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Moss almost abandoned acting for another spotlight.

She spent much of her childhood training to be a ballerina and was poised to take it up as a career. But at age 15, the time most dancers turn professional, she was offered a part in the movie “The Joyriders,” starring Martin Landau.

“I couldn’t do both,” she said, speaking from the home that she shares with her fiance, “Saturday Night Live” star Fred Armisen. “I kind of made this adult decision. I guess I thought that the life of an actor is longer and there’s less chance of failing. I mean, the only thing riskier than acting is ballet.”

The dance lessons have paid off in other ways. Moss brings a ballerina’s sense of discipline, timing and concentration to her work. Co-workers and writers repeat the same compliment: She’s a “present” actor, always in the moment, even if that moment is 1962.

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“I can watch her in a scene that I wrote and edited and seen a hundred times and still be surprised by her behavior,” Weiner said. “It makes the other actors better.”

It also made the second season of “Mad Men” more impressive than the first. Peggy’s arc – a young woman with great integrity in the workplace, all while foisting her baby off on her mother – cemented the show’s overall theme: Anyone who leads a double life is risking double the trouble.

“She’s not a hero,” Moss said. “She’s made huge mistakes. She’s flawed. She sort of stumbles along sometimes.

“I like that she’s very real. I like the fact that she dresses like a real woman would at that time. If I wanted to wear beautiful clothes and have my hair nice, I may have done something else.”

Peggy’s sins haunted her throughout last season, leading to the climactic moment in the finale in which she confesses to co-worker Pete Campbell that she had his baby. If Moss does win an Emmy on Sept. 20 – Gold Derby, the primary award tracker, calls her a “devious Emmy contender, but she should be leery of overdue Sedgwick and Hunter” – it will be in large part because of that scene.

Vincent Kartheiser, who plays Campbell, said the scene wasn’t difficult, because the two characters had been building to it for two years. “She was incredibly in the moment,” said the actor. “It’s an amazing performance.”

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Moss said a win would be great because it would give more attention to the show – which won the Emmy for best drama last year following its rookie season – but she’s not spending her free time fretting over an acceptance speech. There’s a new season to film, and Olson still has a lot of growing up to do.

“Everything is pretty normal,” she said. “I’m going to the set. I’ve got to know my lines. I’ve still got to go to work.”

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MAD MEN

When: 10 p.m. EDT Sunday

Where: AMC

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