"This is my first debate," Mulcair said noted Thursday, flanked by his team of Toronto candidates.
Mulcair painted his party as the only alternative to Harper's Conservatives in another pitch to convince Torontonians to vote for the New Democrats.
"I think that it's going to be an opportunity for Canadians to realize that this election is about choice — a choice between four more years of Stephen Harper or an extraordinary team of women and men dedicated to bringing positive change to Ottawa," Mulcair said.
As the only federal leader speaking publicly ahead of the debate, Mulcair said it was great to be back in "Canada's most important city."
Mulcair was in the riding of University–Rosedale, where NDP candidate Jennifer Hollett will be running against Liberal Chrystia Freeland.
Freeland was elected as a Liberal MP during a byelection in the riding Toronto–Centre.