In Canada, a third party has two distinct meanings in the political process. For legal and official purposes, a "third party" refers to agents other than candidates and voters who participate in elections. For example, campaign advertisements funded by groups other than the parties and candidates running may be called "third party advertising". During a campaign period, registered third parties must declare their sources of funding and are restricted in the amounts they can spend in advocating for or against a party or candidate. See Harper v. Canada for the Supreme Court decision upholding the constitutionality of these restrictions in the Canada Elections Act.
The second, formerly popular, definition is derived from the phrase in American parlance: a relatively small federal or provincial political party that is not usually considered to have a realistic chance of forming a government, but has representation in the federal House of Commons or the provincial legislature. While both the Congressional and Westminster parliamentary systems tend to reward two dominant parties or blocs, the ability in the latter for third parties to compete and affect the outcome of elections is a major point of differentiation for Canadian political culture and history. In the US, a "third party" describe any party besides the Democrats and Republicans as regardless of their relative position; in the Canadian context (and for the purposes of this article), it more commonly refers to the largest party that does not form the government or Official Opposition. The efficacy of these parties often depends on whether they qualify for party status and are thus entitled to play a formal role in the legislative process. Since the House of Commons standing orders were amended in 1963 to recognize smaller parties, the third-largest party has always met the criteria for status. However, each legislature has different standards, and this is not always the case.
Like the United Kingdom (on which much of its democratic tradition is based), Canada has been described as a "two and a half" party system, with multiple effective parties, only two of which are contenders for government at any one time, though most provinces have outgrown this definition. During minority government situations, third parties may hold the balance of power, and thus exercise significant control over the government's policy. In some cases, such a party has swept to power by "coming through the middle", as with the emergence of the Social Credit Party of British Columbia in 1952–53.
The official meaning has become more prevalent in recent years, since the current Canadian Parliament has seated members from five different parties, making the usual usage less meaningful.
On the federal level, since Confederation in 1867, the government has been formed alternately by the Liberal Party and the Progressive Conservative, and its successor, the modern Conservative Party. The first notable third party was the Progressive Party, which appeared in 1920 and had a strong showing in the 1921 elections coming second after the Liberal Party. In tune with their character as an agrarian populist party, the Progressives declaimed any interest in power for themselves, seeking instead to defend the interests of farmers against the main parties and big businesses. Though several provincial farmers' parties did form government, the Progressives under Thomas Crerar and Robert Forke refused the role of Official Opposition and worked closely with the Liberal government of the day when they held the balance of power from 1921–26. The parliamentary party had a house leader, but its decentralized nature and firm belief in the responsibility of individual MPs to carry out the will of their constituents made party discipline impossible to maintain. Tension between the conservative and radical tendencies in the party led to its demise. Following the election of 1925 the Progressive Party was effectively split between those who backed the government of Mackenzie King and those who gravitated towards JS Woodsworth and his caucus of Labour MPs. The latter coalesced into the Ginger Group and continued to serve as United Farmers or Progressives, while the conservatives largely joined the Liberal Party proper or sat in its caucus as Liberal-Progressives. Later Liberal-Progressive Premier of Manitoba John Bracken took over the leadership of the federal Conservative Party in 1942 and rechristened them the "Progressive Conservatives." This gave rise to the mistaken, but persistent belief that the two parties merged; there is no relationship between them, as the Progressive Party had ceased to exist a decade earlier.
During the Great Depression two new third parties emerged: the democratic socialist, Co-operative Commonwealth Federation (CCF), formed around the nucleus of the Ginger Group, and the right-wing, Social Credit Party of Canada, which sought reform of monetary policy. Both parties persisted for several decades with varying degrees of success. After a gradual decline Social Credit lost its remaining seats in the 1980 federal election and never recovered. The CCF was reorganized into the social democratic, New Democratic Party (NDP) in 1961 and officially aligned itself with the Canadian Labour Congress. The NDP played a significant role in both Liberal and Conservative led minority parliaments afterwards, particularly from 1963–1968 and 1972–1974. While holding the balance of power, the New Democrats were able to achieve many long-held policy goals (universal medicare, the Canada Pension Plan, and the creation of Petro-Canada as a state-owned oil company) without forming government.
Following the 1993 election, the division between the "main" and the "third" parties started to break down, due to the poor showing by the Progressive Conservative Party and the rise of the Reform Party and the Quebec-based Bloc Québécois. While the Bloc could never form a government because it never contested ridings outside Quebec, the Reform Party and its successor Canadian Alliance had some modest success and eventually merged with the Progressive Conservative Party to form the new Conservative Party which formed the federal government from 2006–15.
The federal election of 2011 saw a further realignment of Canadian party politics as the New Democratic Party made significant gains, allowing it to emerge as the official opposition. For the first time in Canadian history the Liberal Party was reduced to third party status. The Bloc Québécois which had been the third largest party in the House of Commons since 1997 was reduced to only four seats while a new party, the Greens made their debut in the House after winning a single seat. The New Democratic Party returned to third party status in the federal election of 2015.
A number of provinces in Canada have a two-party system (that is, the two major political parties alternate governing, though the identity of these parties may change over time). Provinces west of Quebec have, for most of the 20th and 21st centuries, had a three-party system, though the identity of these parties may have changed over time. For the most part, these are the provincial Liberals, provincial Progressive Conservatives and the NDP.
Provincial parties that may currently be considered third parties are:In Newfoundland and Labrador, the New Democratic Party of Newfoundland and Labrador.
In Prince Edward Island, the Green Party of Prince Edward Island.
In Nova Scotia, the Nova Scotia New Democratic Party
In New Brunswick, the Green Party of New Brunswick.
In Ontario, the Ontario New Democratic Party.
In Manitoba, the Manitoba Liberal Party.
In Saskatchewan, the Saskatchewan Liberal Party.
In Quebec, Coalition Avenir Québec
In The Yukon, the Yukon New Democratic Party
In Alberta, the concept of a third party may be misleading since elections are not typically competitive between even two parties. All of Alberta's past governments formed very long political dynasties, which then disappeared, never to hold power again. In the 2015 election, the democratic socialist Alberta NDP won a majority government, a turn of events widely termed a "political earthquake", given Alberta's reputation as Canada's most conservative province. It would be the first time Alberta was not governed by an avowedly conservative party since 1934. The outgoing PCs had been in power for 44 consecutive years, but were reduced to 10 seats. Defeated Premier Jim Prentice resigned his seat and retired from politics on election night. leaving the Tories as the third party for the first time since 1967. The ensuing byelection in Calgary-Foothills was won by the Official Opposition Wildrose Party. Ric McIver was appointed interim Leader of the Progressive Conservatives for the foreseeable future, thereby deferring what would be the party's fourth leadership convention in less than a decade. Meanwhile, the Alberta Liberal Party, which had alternated between Official Opposition and third party throughout the PC dynasty, lost all of its seats save that of David Swann.
In British Columbia, the British Columbia Liberal Party was the third party from 1953 until 1991, when it eclipsed the British Columbia Social Credit Party. More recently, the Green Party of British Columbia has been considered the province's third party, finishing third in every election since 2001. The Greens captured their first seat in the legislature in 2013 when Andrew Weaver won the seat of Oak Bay-Gordon Head, the first Green win in a provincial election anywhere in Canada. Several other parties have recently been the third party in the legislature. From the 1991 election, in chronological order, these were the British Columbia Social Credit Party, the Reform Party of British Columbia, the Progressive Democratic Alliance, and Democratic Reform British Columbia. Opinion polls for the last election forecast a strong showing for the British Columbia Conservative Party, which had been represented in the Legislative Assembly since a Liberal MLA crossed the floor in 2012, casting doubt on the Greens' future as British Columbia's third party. In the event, the Conservatives were shut out.
Prince Edward Island has only elected two third party MLAs in its history: Dr. Herb Dickieson for the PEI NDP from 1996 to 2000 and Peter Bevan-Baker in 2015 for the Green Party of PEI. The Greens had outpolled the NDP in the previous election, and Bevan-Baker, in his third campaign for the seat, won over 50% of the vote in Kellys Cross-Cumberland .
In Nova Scotia, the mid-1990s saw the emergence of the NDP as a serious contender for government. Both Alexa McDonough and Robert Chisholm expanded the party's base beyond the labour movement and Cape Breton. The Liberals and the NDP won an equal number of seats at the 1999 election; in an unprecedented arrangement, the Speaker ruled that the two parties would split the parliamentary resources of the Official Opposition, and take turns leading the opposition in the Assembly on alternating days. This situation lasted until Liberal leader Russell MacLellan resigned from the legislature, and the party lost his seat to the governing PCs. In 2009. the NDP was elected into government, the first time an Atlantic province had voted for a party besides the Liberals or Conservatives. The Tories were relegated to the position of third party with only ten seats > and the Liberals formed the Official Opposition. Four years later, the NDP were heavily defeated, and reduced to third party status once again, and Stephen McNeil became Premier.
In New Brunswick, the Green Party made a breakthrough in the 2014 election. Party leader David Coon was elected in Fredericton South, though the party secured only 6.6% of the vote compared to 13.0% for the NDP.
In Quebec, polarization over the National Question made it difficult for third parties to be viable. The decline of the once-dominant Union Nationale and the Creditiste movement coincided with the rise of the Parti Quebecois as the bulwark of Quebec nationalism, and the Parti liberal du Quebec's ideological shift to the right to consolidate the federalist vote. As support for sovereignty ebbed, other parties became important political actors. The Action démocratique du Québec, which began as a vehicle for conservative nationalist Mario Dumont, rose to Official Opposition status after the 2007 election, but lost most of its seats and fell back to third place in 2008. The party has since reorganized and rebranded itself the Coalition Avenir Québec under former PQ cabinet minister Francois Legault. The orientation of party politics around ideology rather than constitutional matters (see pour un Quebec lucide and pour un Quebec solidaire) may be the beginning of a durable multiparty system.
Saskatchewan is the only province currently without any third party representation in its legislature, since the Saskatchewan Liberal Party lost its remaining seat in the 2003 election. The Liberals had been the right-wing counterweight to the CCF/NDP from the 1930s, and after the disgraced PC Party collapsed, had returned to official opposition. This success was short-lived, as prominent Liberal MLAs and organizers joined with ex-PCs and supporters of the Reform Party of Canada to form the Saskatchewan Party as a unified centre-right alternative. Struggling to stay relevant, the Liberals nominated only 9 candidates in 2011 and finished behind the Green Party of Saskatchewan in the popular vote. Despite internal disarray, the Greens (who began as a left-wing protest group) were able to capitalize on the flagging popularity of NDP leader Dwain Lingenfelter, who led the opposition to a disastrous nine seats. The Liberals managed to rebound in 2016, nominating a full slate of candidates and more than tripling the popular vote of the Greens, but won no seats.