(CBS News) When Julianne Moore found out she would be playing former Alaska Gov. Sarah Palin in the HBO film, "Game Change," the first thing she did was hire a vocal coach.
"I had her book-on-tape, which she read on tape," Moore told the U.K.'s Daily Mail on the red carpet of the movie premiere. "So I put everything in my iPod. I listened to it when I was running. I listened to it when I was picking up my kids in the car. It was pretty much a constant ... I got the voice down before I started to tackle the physicality."
Based on Jon Heilman and Mark Halperin's book "Game Change," the film chronicles a two-month period in the 2008 presidential race, starting with Palin's nomination as Sen. John McCain's vice presidential nominee and leading up to the election of President Obama.
"Everything is sourced," Moore, 51, said about the film's content. "It's all there on YouTube."
In an interview with Jon Stewart, Moore said director Jay Roach reached out to Palin's team prior to filming, but her people didn't want to have any involvement in the movie.
Palin supporters, however, have beento the movie in the weeks leading up to its release.
Moore added, "We were very very careful to be as balanced as possible in our portrayal ... this is less of a story about Sarah Palin than it is about those 60 days between her pick and the loss."
"Game Change," which also stars Ed Harris and Woody Harrelson, premieres Saturday on HBO.
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