The Borrego Foundation is a grantmaking institution that significantly contributes to left-of-center organizations which share a focus on supporting abortion and environmentalism.  Borrego President Mary E. Rubin is a member of the board of directors for the left-leaning Center for Reproductive Rights, a pro-abortion-rights advocacy group. 
The foundation has invested substantial funds into a variety of pro-abortion advocacy organizations, including Planned Parenthood and the National Partnership for Women and Families.  The group also provides financial support to other left-of-center organizations.
While Borrego makes large contributions in support of abortion advocacy, it also donates to several other left-leaning causes. One large recipient of funding is the left-of-center think-tank Center on Budget and Policy Priorities, which received $75,000 from Borrego in 2016. 
Borrego has also bankrolled the International Rescue Committee (IRC) that directs its efforts towards driving political pressure and on the ground assistance to humanitarian crises, particularly refugees and displaced persons. Currently, the IRC is promoting awareness of the tensions at the United States border with Mexico and highlighting the urgent needs of those seeking asylum. 
The Borrego Foundation was established in the late 1990s by the Lieber family, led by Stephen Lieber, an investor who was described by Fortune as the “king of balanced funds.”  The Lieber family also founded the Essel Foundation in the mid-1960s which has primarily focused on mental health causes due the family’s personal experiences with mental disorders. 
Stephen’s son Samuel Lieber is recorded as the vice-president, secretary, and treasurer of Borrego. Samuel is also the main funding source for Borrego, contributing many hundreds of thousands of dollars to the foundation.  In addition to his work with Borrego, Samuel is the founder and president of Alpine Woods Capital Investors that manages over $4.2 billion regulatory assets. 
Mary E. Rubin is president of the Borrego Foundation and guides investing towards left-of-center organizations that primarily focus on feminist causes. In addition to the aforementioned pro-abortion donations, she has also directed financial support towards the Institute for Women’s Policy Research.  This institute’s interests lie entirely on women’s issues including wage gap inequality and employment discrimination. 
Rubin’s background includes a term as board chair of the left-leaning Nature Conservancy and eight years on the board of directors for Planned Parenthood Hudson Peconic (PPHP). She held multiple roles at PPHP including the chairmanship of fundraising and investment advisory.  In 2018, the New York Times reported that the PPHC-operated clinic in White Plains, New York had allegedly discriminated against a pregnant employee. 
Mary Rubin has made personal political contributions to the campaigns of President Barack Obama and Senator Elizabeth Warren (D-MA).