"I was very nervous," she confessed. "I mean, people are very aware of what she looked like and what she sounded like and what she moved like. And it's challenging because you want to approximate that as much as possible. And luckily there was a wealth of information out there that I could draw from."
Part of that wealth of information was Jackie's iconic fashion. And while Portman says the film, which picks up after JFK's assassination, isn't "particularly about the clothes," she does admit that the costumes helped her to get into character.
"Of course when you wear clothes or hair and makeup for a character it always helps put you in character and in the mood of where you are, so it's helpful," she said.
While Portman promotes her role, she's also been campaigning in support another former first lady, Hillary Clinton.
"I'm very excited to see Hillary become president," she gushed. "And it's of course been a disappointing election cycle to hear the vulgarity as opposed to people talking about the issues, [but] I think Hillary has been great about bringing it back to that when there's a lot of noise."