Layton, of course, died after a battle of cancer just three months after leading his party to 103 seats in the 2011 federal election.
For a lot of Canadians, the loss of Layton touched them deeply.
For some — especially for those on the right side of the political spectrum — his death and subsequent tributes were overblown and over-reported.
[ Related: Canadians react to the Jack Layton biopic ]
For the NDP, it was a personal and professional tragedy. Layton, after all, led his party to its best showing ever in 2011. He was the party patriarch, he was the brand, it was Jack's party.
Over the past two years, they've forged ahead and elected a new leader in Thomas Mulcair.
But have they recovered? Have they moved forward? And what's in store for what's now Tom's party?
Yahoo! Canada News reached out to people both inside and outside the party to get their opinions:
Within the NDP caucus, he's gone but not forgotten:
According to two NDP MPs we spoke to, the memory of Layton is regularly evoked within caucus.
Libby Davies, Member of Parliament for Vancouver East:
Many of us in the NDP Caucus talk about Jack, both new MP's and the veterans, like me. We talk about him often amongst ourselves and in Caucus. What he did; personal memories and stories; and the lighter moments too.
His presence is very much felt. People often say - what would Jack think. Or, remember what Jack said. His legacy is powerful, both for New Democrats, and Canadians from every walk of life. He gave us hope, a positive way of working together, and a belief that when we do work together we can change things for a better world. Jacks presence is many fold, and you'll find photos, leaflets, buttons, and many keepsakes on NDP desks and walls.
He's always close to us.
Megan Leslie, Member of Parliament for Halifax:
We often call up Jack's legacy in our difficult moments at caucus. When the "everyday" pressures of life in the House of Commons become overwhelming, we often find ourselves forgetting the big picture.
It's easy to focus on a few silly questions in question period, and forget that we're there fighting for something bigger, fighting for our shared social democratic vision. When we're in those heated or stressful moments, that's when we'll often talk about Jack, his passion for equality, his doggedness on the housing file, his commitment to the environment. Even the MPs who didn't serve very long with him know these things to be true about Jack: it's why they joined the party and ran for us.
It's been amazing to see in some of our trying times, when a colleague will remind us all of what Jack always said or the advice he would have given us, or of his vision. It's like a collective deep breath happens in the room, and we're able to refocus or recommit, or change direction completely...whatever is needed. It's wonderful, really. It's like he's still there for us. And, well, he is.
In the 2011 election, the New Democrats earned 30.6 per cent of the popular vote.
Aside from a brief honeymoon period after Mulcair took the leadership in March 2012, the party hasn't reached those heights again.
The last Nanos Research poll, from June, had the NDP in third place with 25.3 per cent national support.
Is this Thomas Mulcair's party now?
Over the past two years tributes to Jack Layton have been plentiful. There is now a park, a street and a ferry terminal named after the man. And, on Thursday, there will be an unveiling of a bronze statue of Layton on a tandem bike — donated by the Ontario Labour Federation — on the Toronto Waterfront.
So, yes, it's probably not an easy thing for Thomas Mulcair to live in the shadow of Jack Layton.
But Abacus Data's David Coletto says that while Jack and Tom are two very different personalities, Mulcair has been an effective leader of the opposition.
"[Mulcair's] biggest challenge remains increasing his public profile outside the Ottawa bubble. My only criticism is that the party should have been doing more to increase his profile before the next Liberal leader was chosen. Now, it's tough competing with Trudeau for attention," Coletto told Yahoo! Canada News.
"Tom Mulcair is leader and has a big impact on the party but most of this caucus owes their election to Layton, and Canadian's haven't really got to know Mulcair. So internally the NDP may be Mulcair's party but externally with Canadians the NDP is still far more associated with Layton than with Mulcair."
Political consultant Gerry Nicholls says that it's too early to judge the party under Mulcair.
"He’s done a good job of keeping the party united and on message, plus his performance in the House has been good, but he still has not been tested in real political combat," Nicholls told Yahoo! Canada.
"So yes it’s now “Tom’s Party”, but much will depend on what happens in the 2015 election."
(Photo courtesy of Reuters)
Are you a politics junkie?
Follow @politicalpoints on Twitter!