Traditionally, each riding association of a party holds a special meeting to elect a fixed number of delegates to represent it at a leadership convention.
Because of the implementation of "one member one vote" (OMOV) systems and proportional delegate elections by most parties, conventions have declined in importance.
The Liberal Party of Canada held the first leadership convention in 1919, electing William Lyon Mackenzie King.
Both the modern Conservative Party and the NDP have instituted "one member one vote" systems in recent years.
In 2009 the Liberal Party approved a constitutional amendment requiring future leadership elections to be conducted using a modified OMOV system in which each riding is accorded equal weight.
The New Democratic Party held its most recent leadership election on October 1, 2017, due to incumbent leader Thomas Mulcair having lost a vote on a leadership review at the New Democratic Party's federal convention held in Edmonton, Alberta on April 10, 2016.
The Bloc Québécois held its most recent leadership election on January 17, 2019 and chose Yves-François Blanchet as leader.
The Green Party held its most recent leadership election between September 26 and October 3, 2020 and chose Annamie Paul as leader on the eighth ballot.