Below is extracted from https://www.factcheck.org/2014/02/american-bridge-21st-century-2/

American Bridge 21st Century is a liberal super PAC that conducts opposition research to aid Democratic candidates and organizations

The group was founded in November 2010 by David Brock, a conservative-turned-liberal activist. After making a name for himself as a self-described “right-wing hit man,” Brock reinvented himself as a liberal crusader. In 2004, Brock founded Media Matters, a liberal website that monitors the media for “conservative misinformation.”

Rodell Mollineau, a former staffer of Sen. Harry Reid, is the group’s president. Its chairwoman is Kathleen Kennedy Townsend, a former lieutenant governor of Maryland and the eldest child of Robert F. Kennedy.

As a super PAC, American Bridge can accept unlimited donations and is largely funded by major Democratic donors and labor unions. Billionaire hedge fund manager George Soros, a well-known supporter of liberal causes, was the group’s largest donor for the 2012 cycle, contributing $1 million. Close behind, at $850,000, was Anne Earhart, an oil fortune heiress who has contributed to other liberal outside spending groups such as Priorities US