[1] Clark was elected to the Manitoba legislature in a by-election called in the Mountain constituency after the resignation of high-profile cabinet minister Ivan Schultz.
[2] He defeated Progressive Conservative Marcel Boulic by 276 votes, and served for the next three years as a backbench supporter of Douglas Campbell's government.
Many Liberal-Progressives were concerned with Clark's relatively narrow margin of victory, as Mountain had previously been considered one of the party's safest seats.
Clark received support from the constituency's Anglo-Saxon majority and large Flemish population, while Boulic did well among French Canadians, who made up one third of the electorate.
[3] The Liberal-Progressives were defeated in the 1958 provincial election, and Clark lost to Progressive Conservative Abram Harrison[2] by 238 votes in the redistributed constituency of Rock Lake.