Christian Bale had a choice to make. He'd been hemming and hawing about Adam McKay's very unconventional proposition that he play Dick Cheney in a biopic about the former vice president of the United States, and his deadline to decide was coming up.

"I thought it was going to be impossible. I also didn't want to do that much work," Bale said recently in Beverly Hills. "I just thought, 'this is going to be a lot of work!' Like, 'Do you realize how difficult this is going to be? I don't really want to do that.'"

But he started researching Cheney and doing some early makeup tests and realized he'd become obsessed. Suddenly seeing his name next to Cheney's didn't seem "so completely crazy." He had to say yes.

Besides, he laughed, "There's always attraction, I feel like, in ending a career in one go."

So Bale and, eventually, his frequent co-star Amy Adams ("The Fighter," ''American Hustle"), decided to do the impossible and become the enigmatic Dick and Lynne Cheney for McKay's "Vice." The charged polemic, which arrives in theaters Christmas day, follows the Cheneys from their inauspicious origins to Washington D.C., where Dick Cheney would became one of the most powerful and influential figures in the country.

To Bale, Cheney was someone who thrived on serving someone, whether it be Donald Rumsfeld or George W Bush, but that his first loyalty was to his wife. The film posits a Shakespearean power dynamic where Lynne is pulling strings behind the scenes.

"Lynne was the ambition and the driving force," Bale said. "Times being as they were Lynne was not able to achieve all these goals that she wished she could achieve herself. She needed a man to do that and so Dick became that vessel through which she achieved her own ambitions."

Adams too became fascinated by her character's initiative and intelligence, and realized she needed to stop thinking of her as merely "Dick Cheney's wife."

"My daughter asked me what I was going to play, and I said, 'I'm playing Dick Cheney's wife. And she was like, 'Why are you always playing a wife and a girlfriend?' And I realized even I had assigned her a position that was in relationship to Dick Cheney and it changed the way that I view her," Adams said. "I was like you know what, 'No I'm playing Lynne Cheney. She's married to Dick Cheney. She is his wife, but she has her own identity.'"

Neither met their real-life subject, who they would be portraying over the course of four decades. Bale wanted to but was "warned away from trying to do that."

"It's one of those deals where they say if you bump into somebody, well good, chat all you want, but if you reach out to somebody, it's a different legal thing that happens with that," he said.

But they had a lot of resources to help, including first-hand accounts from people who knew them, and the internet. Bale's phone is still full of videos and photos of Cheney, right alongside those of his wife and kids.

"I haven't been able to get rid of it yet," said Bale, laughing that he's become fond of the memories.

Of course, learning about Dick and Lynne Cheney is one thing, but Bale and Adams would also have to look like them as well for "Vice" to work. For Bale, that meant yet another significant physical transformation that involved wearing fake teeth, gaining some 40 pounds, adding "a couple of inches" to his neck and spending about four hours in the makeup chair every day.

"It helps me get into character, but it doesn't help me live a long life. Really. I've really got to stop doing it at some point," Bale said.

He used to laugh at people who would just opt for an easy fat suit, instead of doing the work, until he realized that Gary Oldman had done just that for his Oscar-winning Winston Churchill transformation for "Darkest Hour." But at that point he had already gained 25 pounds and decided he might as well just keep going. Adams, too gained some weight.

"I found it helpful for just the gravitas that Lynne had," Adams said. "She felt very earthy to me."

One thing Adams struggled with was the long hours in the makeup chair.

"One day I was so tired, I felt like I was on a boat and I was sitting there and we were working late into the night and I said, 'I don't know how you do it, Christian, I really have so much admiration for you,' and he was just like, 'I don't think about it,'" she said. "It's exactly what I needed to hear in that moment."

Although the film itself may be political, both Bale and Adams would rather stay out of commenting on or making judgments about their characters and their politics.

"I didn't approach this with my own opinions. I don't typically head into any character I approach by judging them," Adams said. "That kind of shuts me down in creating the character."

Bale added: "If you're watching us on the screen and you know Amy's political stance on what Lynne was saying and my opinion and how much I disagree or agree with...it really kind of ruins the whole point."

And perhaps the story is more complicated than party lines. Bale said, when you remove the "enormously horrific things," like the Iraq War and enhanced interrogation, you are, "Kind of left with a love story."

"You get this incredibly devoted man who recognizes that he would not have been the person he became were it not for his wife. You get a man who contrary to the times and what was popular with his party, without any hesitation, embraced his daughter Mary when she came out. He didn't give a damn what anybody else thought. But I think also that is largely a part of what makes this story, and any story interesting," Bale said. "There is this desire so often to make everyone into superheroes, to be all villain or all hero and nobody is ... So it's trying to find that balance but hopefully not putting anything of myself into it."

"Does that make sense?" Bale added, "Or does it sound REALLY pretentious?"