Liberal Groups Pressure Mayer to Withdraw From has already lost supporters Musk and Sacks

Yahoo's Marissa Mayer is under pressure from liberal groups to withdraw her support for, Mark Zuckerberg's political advocacy group.

Launched in April with a focus on advocating immigration reform and a long list of Silicon Valley heavyweights, has come under fire recently for currying favor with the causes of conservative politicians in order to win votes. Spending as much as seven figures, the PAC began fronting ads for conservative causes like the Keystone Pipeline and the Arctic National Wildlife Refuge. Trouble is, the ads never mention immigration reform.

Alarmed at the strategy, a coalition of nine liberal grassroots organizations, including Progressive United and Credo, launched a boycott of Facebook, raised a lot of fuss and got a lot of press. As a result, Zuckerberg's PAC took a hit, losing two of its big-name supporters, Tesla Motors co-founder Elon Musk and David Sacks, the CEO and founder of Yammer (acquired last year by Microsoft).

To persuade Mayer to dump the PAC, Progressive United and Credo have ramped up their campaign targeting supporters. They emailed 120,000 of their members who hold Yahoo email accounts, to encourage them to call Mayer to resign as co-founder of Zuckerberg's group. The group also launched a blog on Tumblr (purchased this week by Yahoo), "Drop It, Marissa." A Facebook page is also targeting Mayer.

"Even as other tech stars are resigning from over climate, Yahoo CEO Marissa Mayer is out there publicly defending the organization and its pro-Keystone XL propaganda," said Becky Bond, Credo's political director.

Yahoo was not immediately available for comment.