Clark was first elected to the Alberta Legislature in a by-election held in the central Alberta riding of Didsbury on November 30, 1960. The by-election was made necessary by the death of the previous member, James Owens. Clark won with twice as many votes as Liberal candidate J.A. Lore. He thus became the youngest Alberta MLA at the age of twenty-three years. Ahead of the 1963 Alberta general election, Clark's riding was largely merged with nearby Olds to form Olds-Didsbury. The merged riding was mostly Clark's territory, and he won the new district in a landslide over two other candidates.
Clark was chosen Official Opposition leader by the Social Credit caucus in September 1973 after James Henderson left the caucus to sit as an independent. He had earlier run for the leadership of the party and had the support of half the party's MLAs, but was defeated by Werner Schmidt, who did not have a seat in the legislature. Schmidt led the party to a very poor showing in the 1975 general election. The Socreds lost 23% of its popular vote and fell from 25 to four seats in the Legislature, barely holding onto official status. Clark easily defeated two other candidates with a large majority in his home district. Schmidt resigned shortly after the election, and Clark took the leadership unopposed. In six years as opposition leader, he made little headway on the Tories under Peter Lougheed, who had rapidly built up a machine that dominated Alberta politics as Social Credit had done in its heyday. Under Clark, Social Credit earned a larger share of the popular vote in the 1979 general election, but failed to win more seats. In his home district he won with the biggest plurality of his career as he remained personally popular. Less than a year after the election Clark resigned as Social Credit leader, and resigned his seat on November 30, 1981. The separatist Western Canada Concept won his former riding by a resounding margin in the subsequent by-election. Olds-Didsbury was located in an area that had long been Socred heartland; the Olds half had been in Socred hands for all but one month since the party's 1935 breakthrough, while the Didsbury half been in Socred hands for all but four of the previous 46 years. This marked the beginning of the end of Social Credit as a force in Alberta politics. In a snap election held a year later, Social Credit lost its remaining seats in the legislature, never to return.
After politics
After leaving political office, Clark became a consultant for Hill and Knowlton and Public Affairs International. He served in both those roles from 1981 to 1992. In 1986 he became a member of the Board of Directors and later Chairman of the Board for the Special Waste Management Corporation. On June 8, 1988, Clark, who had not gone to university, was awarded an honorary doctorate of law degree by the University of Calgary. Clark died in July 2020 at the age of 83.
Public servant
Clark was appointed the first Alberta Ethics Commissioner by the provincial government in 1992. He served in that post from April 1, 1992 to March 31, 2003. He also served as Alberta's first Information and Privacy Commissioner from 1995 to 2001. On March 12, 2002 he was appointed Chairman of the Alberta Electoral Boundaries Commission. In 2003 Clark was given the Alberta Lieutenant Governor's Award for his dedication to public service. After resigning from his post as Alberta Ethics Commissioner he worked as the Ethics Advisor for the Alberta Energy and Utilities Board from 2002 until 2007. Since 2006 he has worked as the Chair of Rural Alberta's Development Fund.
