On how many occasions did a Prime Minister lose his or her seat in a general election?
A Prime Minister has lost his seat in a general election on 5 different occasions:
The Rt. Hon. Arthur Meighen, while Prime Minister from July 10, 1920 to December 28, 1921, lost his Portage la Prairie, Manitoba seat in the December 6, 1921 general election. With the defeat of the Government in the general election, Meighen resigned from office. He was however re-elected to the House of Commons in a January 26, 1922 by-election for the riding of Grenville, Ontario.
The Rt. Hon. William Lyon Mackenzie King, while Prime Minister from December 29, 1921 to June 28, 1926, lost his York North, Ontario seat in the October 29, 1925 general election. King did not resign from office and was re-elected to the House of Commons in a February 15, 1926 by-election for the riding of Prince Albert, Saskatchewan.
The Rt. Hon. Arthur Meighen, while Prime Minister from June 29, 1926 to September 24, 1926, lost his Portage la Prairie, Manitoba seat in the September 14, 1926 general election. Following the defeat of the Government in the general election, Meighen resigned from office.
The Rt. Hon. William Lyon Mackenzie King, while Prime Minister from October 23, 1935 to November 14, 1948, lost his Prince Albert, Saskatchewan seat in the June 11, 1945 general election. King did not resign from office and was re-elected to the House of Commons in an August 6, 1945 by-election for the riding of Glengarry, Ontario.
What happens if a Prime Minister (or Party Leader) loses his or her seat in an election?
"... the prime ministership (premiership), like the parties, is not created by law, though it is recognized by the law. The Prime Minister is normally a Member of the House of Commons (there have been two from the Senate, from 1891 to 1892 and from 1894 to 1896). A non-Member could hold the office but would, by custom, have to get elected to a seat very soon. A Prime Minister may lose his or her seat in an election, but can remain in office as long as the party has sufficient support in the House of Commons to be able to govern, though again, he or she must, by custom, win a seat very promptly. The traditional way of arranging this is to have a Member of the party resign, thereby creating a vacancy, which gives the defeated Prime Minister the opportunity to run in a by-election. (This arrangement is also followed when the Leader of the Opposition or other party leader is not a Member.)"
http://www.parl.gc.ca/ParlInfo/Comp...dings/TriviaPrimeMinisters.aspx?Language=E#10
