She first entered politics as a city councillor for Surrey City Council. In 1983, she was elected as a member of the Legislative Assembly of British Columbia as part of the Social Credit Party, representing the provincial riding of Surrey. She was reelected in 1986 in the newly-created riding of Surrey-Newton and became a cabinet minister under Premier Bill Vander Zalm, serving in various portfolios. She had previously served under Vander Zalm when she was a councilor and he was the mayor of Surrey. Vander Zalm appointed Johnston deputy premier in 1990. When Vander Zalm resigned, on April 2, 1991, Johnston was named interim leader of the party. As such, she was appointed premier on April 2, 1991, making her Canada's first female premier. At a Social Credit party convention in July 1991, she was formally elected leader of the BC Socreds in an upset, defeating the favoured frontrunner Grace McCarthy. However, she had little time to implement any new programs since she faced a statutory general election in October. The party was also bitterly divided because of the leadership contest, and it had little time to repair the breach before the writs were dropped. Johnston's long association with the scandal-plagued Vander Zalm significantly hampered her prospects of winning election in her own right, and she was soundly defeated by the New Democratic Party, led by Mike Harcourt. Moreover, many moderate Socreds switched their support to the previously moribund BC Liberals. The Socreds lost more than half of their popular vote from 1986 and were cut down to seven seats, falling to third place in the Legislative Assembly behind the NDP and Liberals. Johnston herself lost her own seat to the NDP's Penny Priddy by over 10 points, and all but seven members of her cabinet were defeated. Harcourt later said that he preferred facing Johnston rather than McCarthy, believing McCarthy would have been a tougher opponent in a general election. Johnston resigned as leader of the Social CreditParty onJanuary 11, 1992 and was replaced by McCarthy. After her defeat, Johnston retired from politics and has had a low public profile. She returned to public life in 2009 as an advisor for the British Columbia Conservative Party.
