Filante first won election to the Marin-Sonoma based 9th district in the California State Assembly in 1978 by defeating Democratic incumbentMichael Wornum. Thanks to his moderate voting record, Filante became a pro at winning crossover votes, enough to hold his left-leaning seat with relative ease for 7 terms. In 1992 he vacated his assembly seat when he ran for election to the Congress.