Ganz was born on March 14, 1943. At the age of three, he moved to Germany with his father, a rabbi, and his mother. Several years later, the Ganz family moved back to the United States, anchoring themselves in Bakersfield, California. Throughout his childhood Ganz witnessed the farming community at work as a resident of the San Joaquin Valley. In 1960, Ganz entered Harvard University but left one year shy of earning his degree in 1964. That year, he went to Mississippi to participate in the Freedom Summer voter registration drive, becoming a field secretary with the Student Nonviolent Coordinating Committee (SNCC).
In late 1965, Ganz joined César Chávez and the UFW. Over the course of the next decade and a half, Ganz became director of organizing and later a member of the national executive board. It was Ganz, more than any other UFW leader, who developed the political tactics that gained increasing voter participation by Mexican Americans in California.
Ganz left the UFW in 1981 and formed an institute to recruit, train, and develop organizers. Over the years, he worked with mayoral, congressional, senate, and presidential campaigns, including that of Barack Obama, developing new techniques for mobilizing citizen participation and strategies for grassroots campaigns.
In 1991 Ganz returned to Harvard, completed his undergraduate work in American history and government, and graduated magna cum laude in June 1992. He continued his studies at the Kennedy School of Government, where he earned an MPA in June 1993 and began to teach organizing. He joined the faculty in 2000 upon completing his PhD in sociology at Harvard. Ganz has taught community organizing and trained individuals involved in community-based organizations, advocacy groups, and unions.
In 2009, he published Why David Sometimes Wins: Leadership, Organization, and Strategy in the California Farm Worker Movement. Ganz dedicated the book as follows: "To the organizers who, with helpful heart, critical eye, and skillful hand, bring us together to change ourselves, our communities, and our world." Ganz currently serves as a senior lecturer at the Kennedy School for Government at Harvard.
Pawel, Miriam. The Union of Their Dreams: Power, Hope, and Struggle in Cesar Chavez’s Farm Worker Movement. New York: Bloomsbury, 2009; Ganz, Marshall. Why David Sometimes Wins: Leadership, Organizing, and Strategy in the California Farm Workers Movement. New York: Oxford University Press, 2009; Griswold del Castillo, Richard, and Richard A. Garcia. Cesar Chavez: A Triumph of Spirit. Norman Oklahoma: University of Oklahoma Press, 1995.