The actresses star in a new clip released by liberal activist group Move On, where they warn against Republican Mitt Romney's pro-life stance and promise to cut funding to Planned Parenthood.
Johansson offers a message to American women: "If you think this election won't affect you and your life, think again... Vote for Barack Obama."
Longoria has been very involved with Obama's re-election bid and currently serves as one of his campaign's national co-chairs.
Washington and Johansson both spoke in favour of Obama at the Democratic National Convention in North Carolina in September.
Bruce Springsteen is also campaigning with former US President Bill Clinton for the Obama campaign in Ohio and Iowa today (October 18).
The US presidential election is held on November 6.
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