'Jackie' screenwriter: 'I didn't feel like she had ever gotten enough credit for understanding intuitively ... the power of imagery and iconography'

Jacqueline Kennedy did not have a conventional speaking voice. It's part New York, part prep school Mid-Atlantic, and it's jarring to most modern ears. Natalie Portman remembers her first few days on the set of "Jackie," going all in on that very specific accent and looking up to see her director Pablo Larrain's wide-eyed bafflement.

"Pablo's face was like 'Uhhhhh...'," Portman said laughing.

They were filming a recreation of the television special "A Tour of the White House with Mrs. John F. Kennedy," where CBS News correspondent Charles Collingwood followed the first lady around with cameras as they spoke about each room and her pricey restoration. Larraín stopped during one take and played footage of the actual tour just to check. He was amazed at how spot-on Portman's interpretation actually was.

Still, "at the beginning, it was shocking," Larrain said.

It was also, he notes, different from how Jackie Kennedy sounded in other circumstances. She had a public voice and a private voice, which Portman was able to study through Kennedy's recorded interviews with Arthur Schlesinger, Jr.

The film "Jackie," now in theaters, explores the nuances of these public and private sides of the enigmatic figure in the immediate aftermath of the assassination of her husband in 1963 as she plans the funeral, exits her home, comforts her children, and tends to her husband's legacy.

It's what compelled screenwriter Noah Oppenheim to make her the subject of his first script.

"Most often she is perceived through the lens of being this style icon, this beautiful woman at her husband's side. People are fascinated by their marriage and his infidelities. But I didn't feel like she had ever gotten enough credit for understanding intuitively the power of television, the power of imagery and iconography, and her role in defining how we remember her husband's presidency," Oppenheim said.

It was she, a week after the assassination, in an interview with Theodore H. White for LIFE magazine, who first uttered the word Camelot in reference to their time in power.

"I always assumed that the Kennedy administration had been referred to as Camelot from the beginning, that they were this young, handsome couple and American royalty," Oppenheim said. "The fact that she came up with Camelot is incredible. That one reference accomplishes more than any list of policy accomplishments ever could have in terms of cementing in people's minds who Jack Kennedy was."

The film, however, isn't out to provide answers. It relishes in Jackie being this inscrutable figure, showing the subtle differences in her interactions with the people around her, including a priest (John Hurt), the journalist (Billy Crudup), her longtime friend Nancy Tuckerman (Greta Gerwig), and Bobby Kennedy (Peter Sarsgaard).

"(Oppenheim) told her story through these different relationships and the different roles she played around the people in her life at different times. I think that's really powerful ... Consistency or arc is really a narrative fiction. Human beings are not like that," said Portman, who is earning some of the best reviews of her career for her performance.

Larrain wouldn't do the film without Portman. The script had been around since 2010 before getting the attention of Darren Aronofsky, who was set to direct his then-fiancé Rachel Weisz in the role. After exiting, Aronofsky stayed on to produce and was the one who made the somewhat unconventional ask of Larrain, a Chilean filmmaker, to consider it.

When Portman met with Larrain, she said it was akin to "being dared" to do the film.

"He was like, 'We're going to do this together or we'll both walk away,'" she said. "I was like 'All right, this is good. Let's take each other's hands and jump.'"

The tone, thanks to studied editing of Sebastian Sepulveda and a striking score by Mica Levi, can sometimes seem more like a psychological thriller than a conventional character study. Larrain delights in the beauty of bringing an audience to "that indeterminate place."

Portman, on the other hand, knows she's at the disposal of her directors and often isn't aware of the exact tone until she sees the finished product.

"When we were making 'Black Swan,' I thought I was making a completely different movie from the one I saw. I thought we were making something almost like a documentary and then I saw it and I was like 'What? What is this?!' I literally had no idea," she said. "I thought it was like a realistic portrait of a psychological breakdown of a person and it was not at all. You can totally misunderstand tone, but still it can work."

The film, heavy with historical and emotional significance, did allow for some levity, though, compliments of that White House Tour.

"We enjoyed that so much," Larrain said. "It was just talking about furniture and chairs. And she would even make the same mistakes Jackie did."

Portman: "We laughed a lot. Pablo kept being like 'Be more excited about the chair!' She's REALLY excited about the chair."

Larrain: "But it was necessary because it shows a kind of splendor. I think when you are portraying such a tragic and critical moment, you need to have splendor to really understand that."