The 2011 Canadian Federal Election, a landslide reelection for the Conservatives following the collapse of the Liberal Party of Canada ended up as a coalitional blip in Canadian history that temporarily resulted in the LPC and NDP switching places as a third party in the House of Commons and Largest opposition party respectively.
Following political miscalculations in trying to force Harper's minority government out of power by assembling a Liberal-NDP coalition with Bloc Québécois support and attempting an unwanted early election in 2009—following two controvercial Prorogations of Parliament—the opposition Liberal Party led by Michael Ignatieff wasn't in a strong position heading into the 2011 Federal Election.
This, coupled with the CPC constantly attacking Ignatieff as an opportunistic intellectual who had tended to live outside of Canada, but now wanted to lead it ended up reducing Ignattieff to a third place showing in the polling, leaving the election between the incumbent PM Harper's conservatives, and Jack Layton's NDP.
Coupled with a strong NDP campaign, which thanks to Layton's popularity—and Ignatieff's unpopularity—was able to surge and make a strategic voting argument to both Liberal and Bloc Québécois voters that only by voting NDP could one stop a Harper Majority Government
This, plus a folksy upbeat style by Layton—ignoring the partisan exchanges between Harper and Ignatieff, & hamstringing Ignatieff at the leaders debate with the zinger 'if you don't show up for work, you don't get a promotion'—a dig at Ignatieff's poor attendance record in the House of Commons—allowed Jack Layton to become the most successfull NDP leader in its history.
However, the biggest winners of the election were Steven Harper's Tories—campaining against the potential for an NDP-Liberal-Bloc Québécois coalition, denouncing the unpopular election as unnecessary, and touting his strong handling of the 2008 Financial Crisis—rode the Liberal's collapse in most of Canada to a Majority Government.
Unfortunately for the NDP, the election would turn out to be a blip as Jack Layton would die a few months after the election. In part from this, and the selection of Tom Mulcair, the Liberals would get a resurgence under the leadership of MP for Papineau Justin Trudeau—who would go on to win the 2015 election.