Wednesday, 20 Jan 2016 09:41 PM
The website said it united people as diverse as worker movement leaders, actors, teachers, farmers, students, poets and heads of companies.
"We believe Trump is a grave threat to democracy, freedom, human rights, equality and the welfare of our country and all our people," the campaign said.
"History has shown us what happens when people refuse to stand against hate-filled leaders. We pledge ourselves to speak out in every way possible against the politics of hate and exclusion he represents."
Nearly 1,200 people had added their signatures to the campaign within hours of it going live on Wednesday.
Jodie Evans, a documentary film producer and cofounder of the anti-war organization Code Pink, said the initiative had arisen out of a conversation with Ensler and said the celebrity endorsements had come from their friends.
"The media is pushing the hate of Donald Trump like it's a reality show," she told AFP.
The third cofounder is law professor Kimberle Crenshaw.
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