"It doesn't really feel effective to me to go out there as an actor and say my opinion about a candidate," the actress told CBSNews.com. "I'm more effective with that in my personal life. Publicly I want everyone to be involved in the process."
The Oscar-winner has recorded a PSA for the non-partisan League Of Women Voters, in a campaign to promote the League's vote411.org Web site.
"I always felt like voting is not a privilege - it's a responsibility," she said. "Maybe that was just the way I was raised."
Madsen said that in the past, she's been saddened by what she saw as a growing apathy around the country and couldn't understand why it seemed some people felt like their voice didn't matter.
Now, she said, things are looking up.
"This year I've really seen this changed and that was so exciting for me, that people were lining up for the primary, that just made me so proud of my country," she said.
The voting awareness campaign is sponsored by the makers of Botox, for whom Madsen is a paid spokeswoman.
Madsen was offered the mouthpiece job after she'd been talking openly in interviews about her use of the anti-wrinkle treatment.
"I was like, 'why are we supposed to be hush-hush about plastic surgery or these products?'" she said. "Why are we supposed to be embarrassed? This all comes from old stigmas that were attached (to aging)."
She said that she only accepted the gig as a spokeswoman because her focus has been to promote the safe use of the product.
"I really didn't feel comfortable saying 'yay' I use it, I wanted to say what my experience with it is." said Madsen. "It's not just your beauty, it's your health and we really have to take care when it comes to our health with all the choices that we make."
Look for Madsen to appear in a multi-platform campaign for the product beginning this week on television, in print and on the Web.
As for acting, Madsen's next big project is a film about aviator Amelia Earhart opposite Hillary Swank in the title role. Madsen plays Dorothy Putnam who, along with her husband, befriended Earhart.
"Dorothy and George Putnam were great friends with Amelia. They had a 20-year marriage and it just sort of petered out," she said. "Dorothy was having a fabulous time with a much younger man - a woman ahead of her time - and so George and Amelia became more romantic after their marriage was over. It certainly would not be any part of the truth if they wanted to depict Amelia as stealing somebody's man because she was so not that and she and Dorothy were great friends."
The film is directed by Mira Nair ("Monsoon Wedding").
"She's a very inspiring person to be around and really the only one who could direct this film just like Hilary is the only one who could play Amelia," she said.
Madsen said it's still difficult for women of any age to find good roles in Hollywood.
"The younger women may have the abundance of parts, but they rarely get to play three-dimensional characters or realistic women," she said. "I went through that and I remember how uncomfortable it was to play the little ingénue because it was really hard to find something real, to find a role that you had something to say."
She said there are juicier roles for more mature women, but there aren't many jobs there either.
"They are not telling our stories. I think men are fascinated with women, I don't know why they don't make more movies about us," she said. "There's always hope and there are good movies being made. I see that when there's rules to be changed, women often change the rules for themselves."