In the 1960s, McCarthy was a popular elected member of the City of Vancouver Parks Board and instrumental in the creation of the VanDusen Botanical Gardens.
In 1968, she successfully lobbied both the Canadian federal and British Columbian provincial governments to broaden home ownership credit legislation to include single, divorced and widowed women without the need for a male guarantor.
After the Socreds returned to power in the 1975 election, McCarthy became a senior cabinet minister, serving in a variety of portfolios, under Premier Bill Bennett.
In addition, her many achievements included the following: lobbied to bring Expo 86 to Vancouver; established Canada’s first linear parkway and SkyTrain; negotiated lighting on the Lions Gate Bridge; spearheaded construction of the Vancouver Trade & Convention Centre at Canada Harbour Place; initiated Canada’s first toll-free help line for abused children; brought the most comprehensive legislation to stop child abuse in the country; and initiated, alongside Justis Greene, BC’s first film promotion office, the Creative BC Film Commission.
[4] However, in a shuffle following the 1986 election, McCarthy gained responsibility for international trade but lost the deputy premier title, which she admitted left her a little disappointed.
[5] On July 6, 1988, McCarthy resigned from cabinet, in protest of Vander Zalm's leadership and the interference of "arrogant" civil servants in the premier's office.
[6] After a series of scandals and discontent within caucus led to Vander Zalm's resignation in 1991, McCarthy entered the 1991 leadership election to succeed him.
NDP leader Mike Harcourt further stirred the pot by claiming that he preferred Johnston over McCarthy, asserting his belief that the latter would be a much tougher opponent in an election.