Former New Democrat MP Olivia Chow is launching a bid to re-enter federal politics, saying she will champion a $15-a-day national childcare program if the NDP forms government in the fall.

Chow, flanked by Opposition Leader Tom Mulcair, announced Tuesday that she is seeking the NDP nomination in the Toronto riding of Spadina-Fort York.

Chow represented the riding – currently called Trinity-Spadina -- for nearly nine years, but resigned her seat in the House of Commons last year in order to run for mayor of Toronto. She came in third place behind John Tory and Doug Ford.

At the morning news conference, Chow said Mulcair is “ready to deliver change” to Canadians, and that she will “bring my leadership and experience” as part of that change.

“After 10 long years of Stephen Harper, his plan just isn’t working,” Chow said.

Mulcair said he “couldn’t be happier” that Chow is re-entering federal politics. The NDP Leader called her a “strong, dedicated” advocate for child care who would also fight for stable funding for public transit.

Chow was a Toronto councillor prior to her first foray into federal politics. Her husband, Jack Layton, was leader of the federal NDP until his death in 2011.

In light of her bid, Chow said she would be taking a leave from her role as a distinguished professor at Ryerson University.

Chow is expected to easily win the NDP nomination for Spadina-Fort York. Her main challenger for the seat will be the riding’s incumbent, Liberal MP Adam Vaughan.

Vaughan won Chow’s seat in a byelection following her resignation in 2014. He defeated NDP candidate Joe Cressy by 6,745 votes.

At news conference Tuesday afternoon, Vaughan said he was undaunted by the prospect of a campaign battle against Chow.

"I have run up against the NDP in every campaign and I've won," said Vaughan. "Olivia Chow and the NDP have never given me a free ride in this part of the city and I've prevailed," he added.

The MP previously served as a city councillor for Trinity-Spadina between 2006 and 2014.

Vaughan, who is also a former journalist, touted his ability to deliver affordable housing, transit improvements and other community services during his tenure on city council and as an MP.

"I have delivered for downtown residents for almost 10 years as a politician and I'll put my record up against almost anybody," said Vaughan.

Vaughan also criticized the NDP's proposed national daycare program, comparing it to former Toronto mayor Rob Ford's hardline favouritism for subways.

"It is a great slogan, we all understand their slogan … but what the NDP doesn't tell you is that it requires $3 billion of provincial money … just to make it happen in eight years' time," said Vaughan.

"Daycare from the NDP is about as elusive as a subway from Rob Ford," he said.

He added that the people should "stay tuned" as the Liberals will unveil their own child care programs.

The new riding of Spadina-Fort York will expand the area contested by the two candidates to include much of Toronto's downtown core, the waterfront and the harbour islands.