Robert Borosage was born in Ohio in 1945 and grew up in Michigan. He graduated from Michigan State University with a B.A. in political science in 1966. He earned a master’s degree in International Affairs at George Washington University in 1968, and a Juris Doctor from Yale Law School in 1971.

He is reputed to have been a New Left radical (DiscoverTheNetworks.Org) during the 1960s or '70s, but his name does not appear in any publication as being connected to the Students for a Democratic Society (SDS), or other authentic New Left group. That said, Borosage's beliefs clearly mirror those of New Left icon Professor C. Wright Mills. particularly Mills' The Power Elite (1958).

In 1974 he founded the Center for National Security Studies, helped write and edit two books, "The CIA File" and "The Lawless State" (with Morton Halperin and two others). He also represented the Institute for Policy Studies (IPS)—America’s premier far-left think tank and stolid opponent of U.S. policy—in a lawsuit against investigations by the Nixon administration. He won a significant settlement.

In 1979, he became director of the IPS, which was founded in 1963 and initially funded by socialist turned capitalist Samuel Rubin, from the fortune he made as founder of Faberge Perfumes, daughter Cora Weiss, and Sears heir Philip Stern, among several others.

In 1988, Borosage left IPS to serve as senior issues advisor to the presidential campaign of Jesse Jackson. He also worked with the late Senator Paul Wellstone and Senator Tom Harkin, as well as Congresswoman Carol Mosely Braun. In 1989, he founded the Campaign for New Priorities, a consortium mostly calling for reduced defense spending.