A member of the Democratic Party, Katz served in the California State Assembly for the 39th district from 1980 until 1996.

He also ran in the 1993 Los Angeles mayoral election, with James Carville serving as a consultant for his campaign.

Katz attempted a legislative comeback in 1998, narrowly losing the primary for the 20th Senate district to LA City Councilman Richard Alarcon.

[3] Katz was a major proponent of the San Fernando Valley secession movement—cochairing the failed Measure F, an initiative effort that appeared on the 2002 ballot.

[4] An ally of Los Angeles Mayor Antonio Villaraigosa, he was Villaraigosa's public appointee to the Los Angeles County Metropolitan Transportation Authority board and Metrolink board chair.