In most circumstances, a leader who has decided to step down gives extended notice, and a leadership convention is organized to choose their successor.
The outgoing leader remains in the position for the duration of the leadership campaign, and then hands over power to the successor shortly after the convention.
Jack Layton initially took a leave of absence from the leadership of the New Democratic Party in 2011 for cancer treatment, and Nycole Turmel was named the interim leader of the party; Layton died before his intended date of return to office, and Turmel continued as interim leader pending the results of the 2012 leadership election.
Glen Clark was forced to resign the leadership of the British Columbia New Democratic Party, and the premiership, after a criminal investigation against him was announced.
In 1983, Joe Clark received only 66.9 per cent support in an internal leadership review process conducted by the Progressive Conservative Party.
In early 2002, Stockwell Day's leadership of the Canadian Alliance came under criticism due to party infighting.
Like Clark, he thus announced a new leadership campaign in which he would reoffer as a candidate, and John Reynolds became the party's interim leader.
Jean Charest became interim leader of the federal Progressive Conservatives following the party's defeat in the 1993 election, in which Kim Campbell lost her own seat.
Bob Runciman served as interim parliamentary leader, but Tory retained the actual leadership of the party.
He was interim leader from 1923 to 1930 since, due to the party's state of disorganization, there was no leadership convention held in that period to choose a successor to Wellington Hay.
Sometimes an outgoing leader decides to resign immediately in order to ensure party unity, because they have accepted an appointment or chosen to stand as a candidate for (or been elected to) another position.
An interim leader, Nycole Turmel was appointed to lead the NDP on July 28, 2011, while Jack Layton was on a medical leave of absence to fight cancer.
He became the party's full interim leader in 2009 after Tory was defeated in an attempt to re-enter the Legislative Assembly in a by-election.
Louis Plamondon became interim parliamentary leader of the Bloc Québécois on June 2, 2011, at the beginning of the first session of the 41st Canadian Parliament, following the 2011 federal election and the defeat and resignation of BQ leader Gilles Duceppe,[4] while Vivian Barbot succeeded Duceppe as interim president of the BQ.