He served in the California State Assembly from Orange County from 1978 until he resigned in 1995 to take a State Senate seat. He served in the Senate from 1995 until 2004 when he was term limited. While serving in the Assembly, he resided in Brea, CA; however he moved to Fullerton, CA in 1995 in order to be eligible to run for the State Senate.]]
While serving in the Assembly, Johnson made two separate bids for the Assembly speakership against Willie Brown, losing 40-3 in 1988 and 48-32 in 1990.
Johnson has been married to Diane Morris since 1968. They have two grown children, Susan and Molly. Mr. and Mrs. Johnson now reside in the upscale Sacramento suburb of Gold River.