In 1990 Horcher was elected to the California State Assembly from the 52nd district, which covered eastern Los Angeles County including cities the of West Covina, Whittier and Horcher's hometown of Diamond Bar.
Although a Republican, Horcher carved a relatively moderate voting record while in the legislature. His support on many key votes endeared him to Democratic Speaker Willie Brown but made him a pariah among his fellow Republicans. After the 1994 elections, Republicans won control of the California State Assembly by a single seat. Horcher declared himself an independent and voted to keep Democrat Brown in power. Furious Republicans qualified a recall election against Horcher, which voters supported May 16, 1995, and replaced him with Diamond Bar city councilman Gary Miller, who turned out to be a more loyal Republican.
After leaving the Assembly, Horcher held various position in the administration of Willie Brown, who by then had been elected mayor of San Francisco. He served under Brown from 1996 until 2004, when Brown's term ended. Following his service to San Francisco, he returned to a real estate and administrative law practice.