Tradition dictates that the party winning the most seats forms the government. If a party ends up with more than half the seats in the House of Commons, a majority government forms and has control over the House.
But if the party winning the most seats still has fewer than half the total seats, it is likely to form a minority government. This status means that the opposition parties, with their greater number of seats, can block bills from passing. The Opposition can also bring down the government on major matters like the budget.
To govern, the party in power must have the support of the House. When there is a minority government, the Opposition can try to topple it by tabling a non-confidence motion. If the motion wins the majority of votes from members, the government then falls.
When the government is brought down, the House of Commons is dissolved and an election called.
A minority party can unite with another party in the House of Commons to obtain an absolute majority. In such cases, the alliance may be temporary like the Liberal Party and the New Democratic Party in 2005. It may also be a formal alliance whereby the party that agrees to unite obtains positions within the government.
If a party comes to power without winning seats in every province, tradition allows the prime minister to appoint ministers from among senators who are from provinces without a seat. This practice occurred in 1979 and 1980 under the governments of Joe Clark and Pierre Trudeau.
Senators who are ministers aren’t permitted to sit in the House of Commons, but may sit in the Cabinet and on the Priorities Committee.
The prime minister may also appoint an unelected person as a minister. This new minister, however, must be elected as soon as possible in a by-election. If he loses the election, he must resign as minister.