Steve Rosenthal is a close personal friend of Andy Stern; they have shared a New Jersey getaway beach house for over 25 years. Unlike Stern, Rosenthal was born into a union family (1953, New York). His father sold shoes in a union shop in Brooklyn.

Rosenthal attributes his passion for social justice to his religious mother and the Judaic tradition of tikkun olam, "repair the world." He graduated from State University of New York at New Paltz, where he majored in political science and became radicalized against the Vietnam war, volunteering for George McGovern’s presidential campaign.

Rosenthal became New Jersey political director for the Communication Workers of America in 1985. He married a fellow CWA organizer, "a Teamster’s daughter," Eileen Kirlin. They later adopted two children, Ana from Brazil, and Sam from Paraguay.

He left CWA to join Bill Clinton’s presidential campaign in 1991, then served on the Democratic National Committee and in the Clinton administration as Associate Deputy Secretary of the U.S. Department of Labor for two years.

When John Sweeney was elected president of the AFL-CIO in 1995, he invited Rosenthal to come with him as political director. Rosenthal served for seven years and showed himself the leading Get Out The Vote campaign organizer in the labor movement. The door-to-door expertise he gained from the ground up played a key role in the 2004 presidential campaign.