The 2015 Canadian federal election was contested on September 14, 2015 to elect MPs to the Canadian House of Commons. The number of seats in the House was 338, up from 308 in 2011. The election, initially scheduled for October 19, was called a month early upon the recommendation of Prime Minister Stephen Harper.
Harper's Conservatives won a majority of 172 seats, a net increase of six but a disappointingly narrow and vulnerable majority. The Liberals under leader Justin Trudeau won back many seats lost in 2011, largely at the expense of marginal NDP seats and the Bloc Quebecois, but were just barely unable to form the opposition due to the NDP's other gains. After the election, it was the first time that the Bloc Quebecois had zero seats in Parliament, thus completing its collapse following the 2011 elections.
Following the inability of the NDP to oust Harper, Thomas Mulcair was ousted in the 2016 leadership election by left-wing elements led by Brian Topp.