Diefenbaker called a snap election and capitalized on three factors:
Nationally, the Liberals had just chosen a new leader, Lester Pearson, who had given an ill-advised maiden speech in Commons that asked Diefenbaker to resign and recommend the Governor General allow the Liberals to form a government without an election due to the recent economic downturn. Diefenbaker seized on the remark by describing a series of classified Liberal Cabinet documents stating that the economy would face a downturn in that year. This contrasted heavily with the Liberals' 1957 campaign promises.
A turnaround in Quebec: Quebec had been largely Liberal since the Conscription Crisis of 1917, but upon the resignation of former Prime Minister Louis St. Laurent, the province had no favourite son leader, as they had since 1948, and its voters were open to new options. Seeking a greater voice in Ottawa, Quebec Premier Maurice Duplessis's Union Nationale used their party machine to ally with the Tories, allowing Diefenbaker's Progressive Conservatives to win two thirds of the seats in what had been a Liberal stronghold for a generation. While the Liberals finished only four percentage points behind the Tories in Quebec, much of their vote was wasted racking up large majorities in their traditional safest seats. Nevertheless, the 25 seats the Liberals won in Quebec accounted for more than half of their decimated caucus, and on a proportional basis was their best performance after Newfoundland.
A collapse in support for the Social Credit Party which lost all 19 of its seats. Prior to the 1957 election, the Socreds were seen as a credible threat to replace the Tories as the main right wing party in the country, as they had done in British Columbia and Alberta, but the popularity of the Diefenbaker government persuaded many Social Credit supporters to abandon their party. This allowed the Tories to pick up not only Social Credit seats, but also proved decisive in many seats that featured a fractured vote between the PCs, Social Credit, Liberals, and CCF. Notably, the Tories swept all seventeen seats in Alberta, where they had previously held just three seats to Social Credit's thirteen. The election proved to be the start of a long decline for the federal Social Credit Party. It would never seriously challenge the PCs dominance in the West again in federal politics, although the BC Social Credit Party governed that province for all but three years until 1991.
National results
Notes: "Previous" refers to standings at previous election, not to standings in the House of Commons at dissolution. * The party did not nominate candidates in the previous election. x - less than 0.005% of the popular vote
