Dressed to maim in a red Halston suit, white chiffon blouse and brown bouffant, actress Jennifer Jones wiggles down a marble corridor in the Capitol. Behind her are a cloud of Yves Saint Laurent's Opium perfume and a few goo-goo-eyed admirers drinking in the vision.

"I have to go see my fellas," she says.

She's played this scene before, prowling the pillared hallways, pounding on senators' doors, a tireless advocate of mental health issues. That day she testified on behalf of NINCDS (National Institute of Neurological Communicative Diseases and Stroke), which is seeking an increase in federal funds for research.

But at 62, she's gearing up for an even bigger part. Bigger than Bernadette of Lourdes (which won her an Acadamy Award in 1943). Bigger than Madame Bovary (1949). Bigger than Ruby Gentry (1952).

Jennifer Jones, widow of Hollywood producer David O. Selznick ("Gone With the Wind") and wife of ultramillionaire California industrialist Norton Simon, wants to play Jean Harris in a film version of the Scarsdale Diet murder.

"I understand the high drama and high trauma of her life, the despair and pain that says, 'I want out.'"

Jones did in fact want out. In 1967 she swallowed a bottle of sleeping pills and wound up lying half-dead in the Malibu surf.

"I don't think I wanted to dies," she says, "no more than she wanted to kill him or herself. These accidents happen."

Jones has optioned Diana Trilling's account of the murder, and says she would be perfect for the part of the emotionally wrought headmistress. No studio or producer has yet snatched the idea.

"I do empathize with the woman," she says, sipping a glass of white wine after a long day on Capitol Hill. She holds the glass in both hands, which shake violently. Her ailment, she says, has been diagnosed as "a benign tremor."

"I feel it's a great woman's part," she says. "It's very powerful. It's almost a Greek tragedy!"

As for the male lead, she says, the part of Dr. Herman Tarnower should be played by "somebody who looks like a lizard. . . . Somebody like Marlon Brando would be interesting."

She laughs. "Of course, he'll probably have to lose a little weight."

Jones also wants to visit Jean Harris in jail. "I don't know how she's going to feel. I don't know how to go about it. I don't know that she'll even see me. I want to do it in a tasteful way. We're not out to do the lady harm. I don't wish to exploit the lady."

Jones says she would like to see Harris financially rewarded. "I would certainly hope that she would benefit. I think if the woman's story is told, she ought to benefit."

The actress, who was last on screen in a 1974 cameo appearance in "Towering Inferno" ("Dreadful. Awful. I was sorry I did it."), doesn't know yet how the screenplay will go, but she says there will be no nude scenes. k

"Not Integrity Jean," she shrieks in mock horror. "And not Integrity Jennifer."

She first became interested in the role, she says, when she read of the case in the newspaper. "I thought it was a fantastic story, a very tragic story. People get trapped in relationships that aren't good for them."

Of course, Jennifer Jones Simon was never really trapped herself, but after all, she reasons, "You don't have to commit murder to understand it."

She was born Phyllis Isley in Tulsa, Okla., the daughter of tent-show operators who toured the rural Midwest. As an aspiring actress, she went to New York, attended the Academy of Dramatic Arts and in 1939 married fellow actor Robert Walker. There were two sons, and dreams of stardom. They went to Hollywood, then came back to New York, where she met a young hotshot producer named David O. Selznick.

"I felt appreciated right from the beginning. I felt totally at ease. I don't know whether that's love at first sight."

In 1942, Selznick introduced her to the world as Jennifer Jones. Reportedly, he had always wanted a daughter by that name. In December, Twentieth Century-Fox chose her to star in "The Song of Bernadette." It was her third picture and first starring role. She was 24.

"I was too young to have success," she says now. "After that first big role, there was a kind of stage fright. I was probably depressed, but I didn't understand what depression was."

Psychotherapy helped. "I've had a lot of therapy," she laughs.

Then Jones divorced Walker, Selznick divorced his wife, the daughter of movie mogul Louis B. Mayer, and the two lovers -- he was 17 years her senior -- were married on a yacht off the coast of Italy in 1949.

She was lucky, she says. "I had good roles, and I had David to guide me." There was "Duel in the Sun," "Portrait of Jennie," "Beat the Devil," "Love is a Many-Splendored Thing," "Good Morning, Miss Dove" and "A Farewell to Arms."

One of her least-favorite roles was Elizabeth Barrett Browning in the 1957 version of "The Barretts of Wimpole Street." "That was not me at all," she says. "That was David's fantasy of me."

The couple had one child. Selznick died in 1965. Two years later, Jones attempted suicide.

"I really don't like to talk about it," she says. "I've never talked about it. It was a massive temper tantrum. I suppose it starts with low self-esteem." Since she didn't leave a suicide note, she says, "I don't think I really wanted to do it."

In 1971 she met Norton Simon. They were married three weeks later.

"He's not interested in movies. Art's his greatest passion," Jones says.

Her life settled down into volunteer work and entertaining, but tragedy struck in 1975 when her only daughter, Mary Jennifer Selznick, committed suicide.

"She jumped off a roof. I think she would have liked to have been an actress. She had been through a depressive period. But she was in therapy, and getting better," Jones says, her hazel eyes reflecting the pain within. "Every time I see a beautiful young girl, I think of my daughter."

But she's also thinking of Jennifer Jones. The woman she calls "just a crazy actress" may be on the verge of a comeback usually reserved for syrupy inside-Hollywood melodramas. As for the prospect of another Academy Award, Jennifer Jones Simon narrows her eyelids, cocks her head and says, not without a trace of irony, "Oh, I think I could handle it." a

She grabs another handful of popcorn. It's allowed, she says, on her diet.

The Scarsdale Diet? "No," she laughs. "The Beverly Hills Diet."