MOVIES : Put Away That Cloth Coat : Joan Allen has been a quietly successful actress for years. Her turn as Pat Nixon in ‘Nixon’ may put an end to the quiet.

Joan Allen is one of those actresses that audiences have seen without realizing they’ve seen. She doesn’t have movie star looks or a marquee name and she disappears into every part so thoroughly that only those in the business know how good she is.

That may all change, however, on Wednesday when Oliver Stone’s newest political epic, “Nixon,” opens. Anthony Hopkins will undoubtedly command the focus for his tortured portrayal of the late president, but Allen, as Pat Nixon, matches him in their scenes together.

Early word on her fierce, subtly nuanced performance has been unanimous that it could make her a star. But that’s a suggestion that fills Allen visibly with alarm.

“I’ve had good feedback about the film but [those raves] are a little frightening,” she says in a very soft voice.

At 39, Allen has the perspective of a self-professed late bloomer, someone who for 12 years has had a nice but understated rhythm going between films (leads in praised non-hits such as “Searching for Bobby Fischer,” “Tucker: The Man and His Dream” and “Ethan Frome”) and theater, performing with the Steppenwolf troupe and on Broadway, winning a Tony for “‘Burn This” and a Tony nomination “The Heidi Chronicles.”

It’s hard to remain inconspicuous in an Oliver Stone movie, however, so Allen knew what she was getting into. She makes an impact actually the second she appears, looking uncannily like the prim former first lady.

It isn’t on view in real life; on this afternoon, Allen looks like the girl next door, if one with rarefied features--pale clear skin, sharp, angular cheekbones. On-screen, though, with brown contact lenses and Mrs. Nixon’s blond bubble hair and taut posture, the similarity is startling.

Stone, for one, certainly saw the resemblance.

“I’d seen Joan on the stage and I knew she was a very good actress but physically, she was stunningly similar,” he says. “She has the same kind of beauty, model-like. And there was a reticence that I liked, a vulnerability, the qualities that Pat Nixon had. Also a tremendous strength, which we don’t know that she had but I suspected she had.”

Perceived parallels aside, though, Allen didn’t feel much kinship with her character or feelings of any kind starting out; she, like much of the country, says she didn’t know a great deal about the former first lady. But she was even more out of touch, she says, given her background.

“I’m very apolitical, I’ve never followed politics to any degree,” she says. “Plus, I’m from a very small town in the Midwest [Rochelle, Ill.], with very apolitical parents. So this really didn’t impact my life. Some friends of mine grew up in the city and went to demonstrations.

“I vaguely remember my father commenting about some people who had chained themselves to some trees at Northern Illinois University and he thought it was a scandal. But I had a life that was very sheltered. Maybe that helped in terms of playing her, because I didn’t have strong feelings about her until I started working on the character.”

Working on the character brought initial frustrations, however, because there wasn’t a great deal of information in the public domain; a research stop at the Museum of Television and Radio brought forth only four pieces of tape of Pat Nixon standing beside her husband waving. Fortunately, Stone’s office had documentary footage, and while reading Julie Nixon Eisenhower’s biography of her mother, “Pat Nixon, The Untold Story,” Allen discovered that there was a short 1972 interview with Barbara Walters, which she obtained and watched over and over, to get the mannerisms and the voice.

“She seemed uncomfortable,” Allen says. “I could see why she didn’t put herself in that position of being interviewed. She seemed lovely but studied, careful about how she phrased things and what she divulged. Very controlled, wanting to say the right things.”

That was the external view; she got more of a sense of the person once she was put in contact with Alexander Butterfield, one of the former players in the Watergate scenario (as a White House aide, he was aware of and testified about the existence of the infamous tapes that brought down Nixon’s presidency) and a technical advisor on the film. “He was the person who helped me the most,” she says. “He wrote me a beautiful note, describing Pat and her mannerisms and how much he really liked her. He knew her quite well--he was the liaison between her and Dick a lot of times, which put him in a very awkward position, it was very strange. But he was tremendously helpful.”

Other observers of the time were involved in research that went into the screenplay. Some of the scenes show a version of the first lady that the country could never have imagined, semi-drunk and furious, lashing angrily at her husband and in one case, asking him for a divorce.

Stone, who has taken a lot of criticism in the past for playing fast and loose with the facts, says he was trying to stay within the borders of the truth this time, using witnesses, staff testimony of overheard conversations and descriptions of their relationship from Julie Nixon Eisenhower’s book.

“We took dramatic liberties and in fact she may never have opened her mouth, there may never have been a squeak out of her,” he says with a laugh. “But we imagined conversations out of hearsay and the staff did hear things here and there.”

Allen remembers the script discussions as having much more integrity.

“Oliver worked tremendously hard to see what she might have been thinking or feeling,” she says. “He would ask, ‘Would she have said this? Would she have said that. . . ?’ ”

When Allen talks about Stone, her face lights up, she struggles to come up with superlatives. Actresses have not always had the same reaction, she knows. But her relationship with him, she says, has been entirely blissful.

“He inspired me, he gave me so much confidence,” she says. “He works with such a passion that I ached to rise to the occasion.” But it also may have been a matter of timing. “A few years ago I would have been too scared maybe, I wasn’t strong enough to have handled it. Taking care of myself on a set came slowly to me. But it was the right time to work with Oliver, and the right time in his life, from what I understand. I’ve heard from people who have worked with him that he’s mellowed in his own life.” (Stone’s reaction: “Oh, perhaps. It’s been a tough couple of years . . . divorces and all that.”)

Still, as she remembers it, the experience began on an intimidating note as she entered the room for the first run-through of the script, the only woman in a room of 30 men. “I kind of gasped,” she says. “But I think that Pat must have felt that way a lot in her life. So it really worked well for the character.”

Rather than succumb to intimidation, though, she played Pat as a fighter, as Stone saw her. “He’d say, ‘Be tough, be tough, remember where she came from. That she’d lost both of her parents to long, agonizing illnesses and she’d taken care of them. She had a very difficult life, a very lonely life.’ ”

The distance between the Nixons is portrayed unflinchingly, with the gulf widening as the Watergate scandal engulfs the president.

“It was a very difficult relationship--he was a strange man,” Allen says. In contrast, her relationship with Hopkins was singular and touching.

“When you work with people who are that good, it makes you so much better,” she says. “All you have to do is look at Anthony Hopkins’ eyes and you get so much, your job is cut in half, there’s so much in his eyes. He was lovely, generous, moving.” Her eyes fill with tears. (She’s having a very emotional day, she explains, but doesn’t want to divulge the details.)

Hopkins, for his part, feels the same about her. “She’s quite fantastic, really, unassuming, very quiet, very shy . . . but the presence was amazing,” he says. “All the men on the set, in the scene on Air Force One, we were all talking about it. James Woods [who plays H.R. Haldeman] said she was amazing, that she was Pat Nixon. I remember watching the scene of the final speech to the White House staff, I was looking at her and she was just like Pat Nixon. Pat Nixon must have been dying up there on that podium and Joan absolutely got it all.”

As Allen admits, this is the first film in which she could really feel her confidence as a film actress growing. Her love affair with acting, however, goes back to childhood, even though, growing up in Rochelle, acting wasn’t a real possibility. But she clearly had a sense of the dramatic.

“Family lore has it that I said to my brother-in-law when I was 5 or 6, ‘Kiss me like they do in the movies,’ ” she says, then blanches. “Oh, that’s going to sound really outrageous.”

Her first foray into acting occurred because she didn’t make the high school cheerleading squad. As a painfully shy adolescent, she expected cheerleading to make her popular. When that failed, she auditioned for a play. After her first performance, she knew it was what she wanted to study and enrolled in the theater program at Eastern Illinois University. The school was more valuable, however, for the friends she made than for the lessons she learned.

One friend who proved invaluable was upperclassman John Malkovich, who asked her if she wanted to join his theater company, Steppenwolf, in 1977.

“We thought she was really talented,” says Terry Kinney, her longtime friend and Steppenwolf colleague. “But we also needed women. We only had three.”

To work with Steppenwolf, she moved to Chicago, considered a radical step in her hometown. Then in 1983, she moved with the company’s esteemed production of “And a Nightingale Sang” to New York. “I remember thinking in my 20s that I would never see New York,” she says. “And I didn’t until then. Perhaps that’s why I can’t leave it. Now that I’m here, I still have a sense of amazement.”

Living in New York also affords her great opportunities for people-watching, while taking her 21-month-old daughter, Sadie, to the playground (her husband, Peter Friedman, is also an actor; they met as co-stars in “And a Nightingale Sang”) or just being out on the streets. That’s one of the reasons she looks forward to a splashy response to “Nixon” with some trepidation. “I don’t know what it’s going to do to my life,” she says. “It would make me sad not to be able to ride a subway or a bus.”

Still, there are trade-offs, as she knows.

“I would like to continue to be able to work on wonderful projects,” she says. In fact, after “Nixon,” she went on to the highly anticipated version of “The Crucible” directed by Nicholas Hytner, starring as the wife of Daniel Day-Lewis.

But as she realizes when she considers the lives of two of her neighbors on New York’s Upper West Side, Kate Nelligan and Mary Elizabeth Mastrantonio, it is possible to get the big roles and still have a normal life.

She smiles slightly. “I guess,” she says slowly, “I could rise to the occasion.”