An interim leader, in Canadian politics, is a party leader appointed by the party's legislative caucus or the party's executive to temporarily act as leader when a gap occurs between the resignation or death of a party leader and the election of their formal successor. Usually a party leader retains the leadership until a successor is formally chosen — however, in some situations this is not possible, and an interim leader is thus appointed by the party's caucus or the party executive. An interim leader may also be appointed while a leader is on a leave of absence due to poor health or some other reason, and then relinquish the position upon the leader's return.
An interim leader has all the rights and responsibilities of an elected party leader, with the exception that the person does not have the discretion to choose the timing of their departure — an interim leader serves only until the party organizes and holds a leadership convention. By virtue of lacking a mandate from the party membership, however, an interim leader is not generally seen as possessing the authority to truly put his or her own ideological and organizational stamp on the party, and is thus effectively limited to a caretaker role in most cases.
There have been a number of instances where instead of a competitive leadership race between multiple candidates, the leadership convention directly ratified the interim leader as the party's new permanent leader, but a convention must still take place in some form.
By convention, if a competitive leadership race between sitting members of the party's caucus is taking place, the interim leader should be a caucus member who is not standing as a candidate in the leadership race, so they do not gain unfair advantage in the contest. Only in rare exceptions, such as when a minor party whose interim leader is also its only caucus member in the legislature or when no no other caucus colleagues are competing for the leadership positions; with rare exceptions, will an interim leader stand as a candidate for permanent leadership.
An interim leader may, if necessary, lead the party into an election, but by Canadian custom, an election is usually not called while one of the parties is in a leadership race.
Practice
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.
However, sudden vacancies may occur for a variety of reasons.
Death in office
Wilfrid Laurier died in 1919, while holding the leadership of the Liberal Party. Daniel Duncan McKenzie was selected as the party's interim leader, serving until William Lyon Mackenzie King was selected as the party's leader later in the year.
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.
Scandal
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. He was succeeded by Dan Miller, who served until Ujjal Dosanjh won the resulting leadership convention.
Creation of a new party
In 2000, after the Reform Party was folded into the new Canadian Alliance, Deborah Grey served as the party's interim leader until the party's first leadership convention selected Stockwell Day. Similarly, after the Canadian Alliance and the Progressive Conservatives merged in 2003, Senator John Lynch-Staunton was named interim leader of the new Conservative Party until the first leadership convention selected Stephen Harper.
Internal dissension
In 1983, Joe Clark received only 66.9 per cent support in an internal leadership review process conducted by the Progressive Conservative Party. Feeling that he did not have sufficiently strong support within the party, he thus scheduled a leadership convention. Initially, he remained the party's leader in the meantime — however, as he was also standing as a candidate in the leadership process, he eventually stepped down and Erik Nielsen was installed as the party's interim leader.