Hollywood actresses are revealing their political allegiances as Democratic presidential nominee Hillary Clinton and the Republicans' Donald Trump square up.

And Susan Sarandon and Sarah Michelle Gellar have made somewhat surprising choices.

'I go by issues: I don't vote with my vagina,' Susan, a long-time Democrat, testily said in reply to a question at an event in Melbourne, Australia, on Sunday, indicating that she might not support Clinton's bid to become the first female president of the United States.

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Swapping sides: Susan Sarandon, left, said 'I don't vote with my vagina,' when asked whether she would vote for Hillary Clinton while Republican Sarah Michelle Gellar will back her

The 69-year-old actress, who looked years younger in a black dress that showed off her decolletage, was at the Breaking Barriers Luncheon at the Crown Towers Hotel when the subject came up.

She was an ardent supporter of Bernie Sanders' run from Democratic nominee and has said she might not vote for Clinton.

Susan has a daughter, Eva, 31, with Italian filmmaker Franco Amurri, and two sons with her longtime partner Tim Robbins, Jack 27, and Miles, 24.

Meanwhile Sarah Michelle, who usually leans Republican, is definitely not going to vote for Trump. The 39-year-old is backing Clinton for the sake of her little girl, Charlotte.

Defying her age: The 69-year-old actress sizzled in a little black dress at the Breaking Barriers Luncheon at the Crown Towers Hotel in Melbourne, Australia where the subject came up

'I’m incredibly proud to be able to look at my seven-year-old daughter and when she says, "Mommy, one day can I be president?" I can honestly say to her, "Yeah, there's a chance that you could," which is not something that my mother could say to me when I was that age.

'I think it’s all about shattering that glass ceiling and understanding that, ya know, we can change the world. Women can, men can, but we all have to work together as a team to do that.'

The former Buffy The Vampire Slayer star shares Charlotte and her four-year-old son Rocky, with husband Freddie Prinze Jr.

Taking the opposite view: Sarah Michelle, who usually leans Republican, is definitely not going to vote for Donald Trump

Backing Hillary: The actress, speaking at an event in Los Angeles, is voting for Clinton so that she can tell her daughter Charlotte, seven, 'Yeah, there's a chance that you could' be president

Sarah Michelle made her case for Clinton at SheKnows Media's three-day BlogHer Conference at the JW Marriott in the LA Live district of downtown Los Angeles on Friday morning in her key note speech.

And she shared a snap of herself on stage, saying: 'I had an amazing morning as the opening keynote speaker at #BlogHer16 Thank you to everyone who attended. I love being surrounded by so much creativity. I left feeling really inspired. #foodstirs #blogher @sheknows.'

SheKnows events are described as 'the world’s largest celebration of women content creators across social media, video, photos, and the web' on its website.