Prime Minister Stephen Harper requested dissolution on August 2, 2015, launching a 78-day campaign — the longest in modern Canadian history — with voting day set for October 19. Harper was seeking a fourth consecutive mandate after nearly a decade in power, having won minorities in 2006 and 2008 before securing a majority in 2011. The extended campaign was widely seen as a strategic choice designed to exploit the Conservatives' fundraising advantage over the opposition parties. This was the 42nd Canadian general election and the first fought under the 2012 redistribution, which expanded the House of Commons from 308 to 338 seats. Turnout surged to 68.3%, up 7.2 percentage points from the 61.1% of 2011 — the highest since 1993 and a sign of the electorate's intense desire to render a verdict on the Harper decade.

Results

The Liberals won a staggering 184 seats with 39.5% of the popular vote — a gain of 150 seats from the 34 they had won in 2011, the largest numerical increase by any party in Canadian federal election history. The Conservatives were reduced from their 166-seat majority to 99 seats on 31.9%. The NDP collapsed from 103 seats and Official Opposition status to 44 seats on 19.7%, their Orange Wave receding almost as quickly as it had crested. The Bloc Québécois recovered modestly from 4 to 10 seats with 4.7% but fell two seats short of the 12 needed for official party status. The Green Party held its single seat with 3.4% of the vote.

The Liberal sweep was geographically comprehensive. The party won all 32 seats in Atlantic Canada — a clean sweep of the region for the first time since Confederation. In Ontario, the Liberals took 80 of 121 seats, dominating the Greater Toronto Area. They won 40 of 78 Quebec seats, reclaiming ground lost to both the NDP and BQ. Even in Western Canada, the Liberals won 4 seats in Alberta — a province that had been a Conservative fortress for a generation.

Party Leaders

Justin Trudeau (Liberal) engineered the most dramatic comeback in Canadian political history, taking his party from third place and 34 seats to a majority government in a single election. When he won the Liberal leadership on April 14, 2013, with approximately 80% support, he inherited a party that had just suffered its worst defeat ever — reduced to third-party status for the first time under Michael Ignatieff. Dismissed by opponents as a substitute drama teacher coasting on his father's name, Trudeau methodically rebuilt the Liberal organization riding by riding. His campaign gamble was audacious: while both Harper and Mulcair pledged balanced budgets, Trudeau announced the Liberals would run modest deficits of under $10 billion per year for three years to fund infrastructure and economic stimulus. The move allowed him to outflank the NDP on the left and claim the mantle of activist government at a moment when the economy was contracting. His campaign's optimistic tone — built around "Real Change" and the promise of "sunny ways," echoing Sir Wilfrid Laurier — offered a deliberate contrast to Harper's decade of disciplined austerity. At 43, Trudeau represented generational renewal against a prime minister who had governed since before the iPhone existed. He won Papineau with approximately 52% of the vote.

Stephen Harper (Conservative) saw his decade-long hold on power broken decisively. Born April 30, 1959, in Leaside, Toronto, Harper enrolled at the University of Toronto but dropped out, moving to Edmonton where he worked in the mail room at Imperial Oil before earning both a bachelor's and master's degree in economics from the University of Calgary. He was present at the Reform Party's 1987 founding convention and served as the party's chief policy officer before winning election in Calgary West in 1993. After leaving Parliament in 1997 to lead the National Citizens Coalition, he returned to politics in 2002 as Canadian Alliance leader, then engineered the historic merger of the Alliance and Progressive Conservatives into the Conservative Party of Canada in 2003. He became the party's first leader on March 20, 2004, and prime minister on February 6, 2006 — winning two minorities before his 2011 majority. By 2015 he was the longest-serving Conservative prime minister since Sir John A. Macdonald. His campaign emphasized economic management and security, but the Senate expense scandal, a contracting economy, and voter fatigue after nearly ten years eroded his coalition. He won Calgary Heritage with approximately 63% but resigned as Conservative leader on election night.

Thomas Mulcair (NDP) entered the campaign as the front-runner and ended it in third place. Born October 24, 1954, in Ottawa, Mulcair studied law at McGill University, earning degrees in both civil law and common law. He served as a Liberal MNA in the Quebec National Assembly from 1994 to 2007, including a stint as Quebec's environment minister under Jean Charest, where he passed legislation enshrining the right to a healthy environment in Quebec's Charter of Human Rights. After a falling-out with the Charest government over a development project in Mont Orford provincial park, he switched to federal politics and won a landmark 2007 by-election in the Liberal stronghold of Outremont. He was elected NDP leader on March 24, 2012, on the fourth ballot, inheriting the 103 seats won by Jack Layton's 2011 Orange Wave. The NDP led in polls through the summer of 2015, and Mulcair was widely expected to become prime minister. His campaign unravelled on two fronts: his pledge to balance the budget in the NDP's first year ceded the progressive-spending ground to Trudeau, and his principled defence of the right to wear a niqab during citizenship ceremonies — while Harper exploited anti-niqab sentiment — devastated the party in Quebec. Mulcair later said the NDP dropped 20 points in Quebec within 48 hours of his niqab stance. He won Outremont with approximately 44% but watched his party lose 59 seats. He was defeated in a 2016 leadership review and replaced by Jagmeet Singh in 2017.

Gilles Duceppe (Bloc Québécois) returned from retirement to lead the party a third time but could not reverse its decline. Born July 22, 1947, in Montreal, the son of acclaimed actor Jean Duceppe, he studied political science at the Université de Montréal before spending years as a trade union negotiator. He became the first Bloc MP elected to Parliament in a 1990 by-election and led the party for fifteen years across three stints, guiding it to 54 seats in 2004. But the 2011 Orange Wave had reduced the BQ to 4 seats and cost Duceppe his own riding. He came out of retirement in 2015 to replace interim leader Mario Beaulieu, but the BQ's recovery was modest — 10 seats, still short of official party status. Duceppe himself lost Laurier-Sainte-Marie to NDP incumbent Hélène Laverdière by roughly 5,000 votes. He resigned as leader days after the election.

Elizabeth May (Green) held her seat in Saanich-Gulf Islands with approximately 54% of the vote. The Greens maintained their single seat on 3.4% of the national vote.

Campaign Issues

The economy dominated the early campaign. Oil prices had collapsed in late 2014, hammering Canada's energy sector and pushing GDP into contraction in the first two quarters of 2015 — technically a recession, though Harper resisted the term. The downturn undermined the Conservatives' core pitch as competent economic stewards and opened space for Trudeau's deficit-spending gambit.

The Senate expense scandal provided a drumbeat of negative coverage throughout the campaign. Senator Mike Duffy was on trial for fraud and breach of trust related to expense claims, and testimony revealed that Harper's chief of staff Nigel Wright had secretly paid $90,000 to cover Duffy's questionable expenses. The trial reinforced perceptions that the Harper government was mired in entitlement and secrecy.

The niqab controversy reshaped the race in Quebec. After a Federal Court ruling upheld a woman's right to wear a niqab during the citizenship oath, Harper appealed and proposed banning face coverings during ceremonies. Mulcair defended the right to wear a niqab — a position consistent with civil liberties but politically devastating in Quebec, where the NDP held most of its seats. The Liberals' more ambiguous positioning allowed them to avoid the backlash that destroyed the NDP's Quebec base.

The Syrian refugee crisis became a defining campaign moment when photographs of two-year-old Alan Kurdi, who drowned attempting to reach Europe, were published in September 2015. His aunt lived in British Columbia. The Liberals pledged to resettle 25,000 Syrian refugees immediately, the NDP promised 10,000 before year's end, and the Conservatives proposed 10,000 over four years.

Notable Outcomes

The Liberal comeback from 34 seats to 184 was without precedent in Canadian federal politics. No party had ever gained so many seats in a single election, and no party had risen from third place to a majority government since Confederation. The result ended a decade of Conservative government and installed the second Trudeau as prime minister, twenty-eight years after Pierre Trudeau left office.

The NDP's collapse from 103 to 44 seats confirmed that the 2011 Orange Wave — built on Jack Layton's personal appeal and a unique alignment of Quebec disenchantment with the BQ — was a one-election phenomenon. The party's Quebec caucus was gutted, falling from 59 seats to just 16.

Harper's resignation capped a consequential prime ministership that had reshaped Canadian conservatism. He had united the right, governed for nearly a decade, and fundamentally altered the country's fiscal and foreign policy — but voter fatigue and a desire for change proved insurmountable. The Atlantic sweep — 32 of 32 seats for the Liberals — was the most complete regional domination in modern Canadian electoral history.