The Mercer Family Foundation is the philanthropic vehicle of Robert Mercer, a mathematician who made his fortune as a director of the hedge fund Renaissance Technologies, and his daughters Rebekah Mercer, Jennifer Mercer, and Heather Mercer.
The foundation came to prominence in the 2016 presidential campaign through the foundation’s donations to the Government Accountability Institute (GAI). GAI supported the research for Peter Schweizer’s book Clinton Cash that examined whether donors to the Bill, Hillary, and Chelsea Clinton Foundation received favors from Obama administration Secretary of State Hillary Clinton or other arms of the government in return for their donations. The book was promoted by for-profit entities which received investments from the Mercer family, including the website Breitbart and Glittering Steel, a production company supported by the Mercer family. Other Mercer Family Foundation grants went to right-of-center advocacy organizations and medical research.
The Mercer Family Foundation was founded by Robert Mercer, a mathematician who, after working for the Defense Department, went to work for IBM. At IBM, Mercer attacked the problem of “machine translation,” or how computers could translate from one language to another. Mercer pioneered the idea of improving computers’ translation ability by creating giant databases, which allowed computers to use statistics to successfully compare words in different languages. One such database included Canadian parliamentary reports in English and French to enable computers to translate between the two. Mercer’s developments paved the way for translation programs such as Google Translate. 
In 1993, Mercer joined Renaissance Technologies, a hedge fund created by mathematician (and major Democratic Party donor) James Simons.  Mercer first came to prominence as a political figure in 2015, when he donated over $11 million to political action committees supporting presidential candidates Sen. Ted Cruz (R-TX) and business executive Carly Fiorina and shifted his support to Donald Trump when Cruz and Fiorina dropped out. 
Mercer’s daughter, Rebekah Mercer leads the Mercer Family Foundation. She sits on the boards of multiple right-of-center organizations, including the Heritage Foundation, the Media Research Center, and the Calvin Coolidge Presidential Foundation.  Rebekah Mercer expressed her political views in a 2018 Wall Street Journal piece, in which she declared her support for “a kind and generous United States, where the hungry are fed, the sick are cared for, and the homeless are sheltered,” and a decentralized federal government where “citizens from smaller federal entities…can determine the majority of laws that govern them.” 
In 2018, 200 scholars, led by controversial environmentalist activist and Penn State University climatologist Michael E. Mann and Texas Tech climatologist Katharine Hayhoe, sent a letter demanding the American Museum of Natural History remove Rebekah Mercer from its 49-member board, saying she funded “anti-science propagandists and funders of climate science misinformation.”  Mercer left the museum’s board in December 2019, after the second of her two three-year terms had been completed. The group Revolting Lesbians praised the decision, saying the museum had removed “a mega-funder of climate science denial.” 
Associations with Steve Bannon
The Mercer family supported three enterprises headed by controversial former Trump 2016 campaign chief executive and Trump administration advisor Stephen K. Bannon. Robert Mercer bought a minority stake in Breitbart News, with the majority being controlled by founder Andrew Breitbart’s widow, Susannah Breitbart.  Another investment was in Glittering Steel, a company that produced documentaries.  Finally, the Mercers invested in Cambridge Analytica, the American subsidiary of a British data-mining firm. 
Government Accountability Institute
The Mercer Family Foundation donated $1 million in 2013, $1 million in 2014, and $1.7 million in 2015 to the Government Accountability Institute, a nonprofit that supported the research and publication of Clinton Cash, a book by Peter Schweizer that showed the relationship between donors to the Bill, Hillary, and Chelsea Clinton Foundation and then-Secretary of State Hillary Clinton. The book alleged that Secretary Clinton granted favors to these donors during her time in government.  Glittering Steel then made a documentary based on Schweizer’s book, which appeared before the 2016 election. The Washington Post reported that in 2013 Steve Bannon simultaneously received $750,000 as CEO of Breitbart News and $100,000 as a 30-hour-a week chairman of the Government Accountability Institute. 
The Mercer Family Foundation gave the Government Accountability Institute $1.8 million in 2017. 
Resignation of Robert Mercer
In 2017 Robert Mercer announced he was resigning from Renaissance Technologies and selling his stake in Breitbart News to his daughters. He announced that he believed in limited government and that “a collection of Individuals making their own decisions within the confines of a clear and concise set of laws that they have determined for themselves will advance society much more effectively than will a collection of experts who are confident in their knowledge of what is best for everyone else.” 
Reclaim New York
The Mercers are major backers of Reclaim New York, which is chaired by Rebekah Mercer and has Jennifer Mercer as a member of the board of directors. The group seeks to stop New York State’s “socialist slide, protect the taxpayer, and fight for the basic freedoms that made New York the Empire State.”  The group urges citizens to file freedom-of-information requests about budgets to increase transparency in counties and cities in New York, provides calculators so New York state residents can see how much they pay in state and local taxes, and provides information about fees imposed by New York counties and cities. According to White Plains Journal News reporter Jon Campbell, Reclaim New York’s “only known funders” are Robert Mercer and the Mercer Family Foundation, which donated $1.8 million in 2017. The group received a donation of $75,000 from Robert Mercer to hire a lobbyist in New York’s state capital of Albany. 
Mercer Family Foundation grants support Convention of States, a nonprofit that seeks to persuade state legislators to support an Article V Constitutional convention calling for new amendments limiting the power of the federal government and requiring term limits on members of Congress. Thirty-four states need to endorse a resolution for a Constitutional convention to happen; as of February 2021, fourteen states had supported the resolution.  The Convention of States is a project of Citizens for Self-Governance, which launched the venture in 2015 with the Mercer Family Foundation providing the initial grant. 
In 2017, the Mercer Family Foundation made four grants of $1 million or more to the Government Accountability Institute, Reclaim New York, the Hospital for Special Surgery ($1,000,000), and the Media Research Center ($2,000,000).