Party leader Jack Layton made the official announcement this Monday at a press conference next to the Westmount Public Library, but Lagacé Dowson's candidacy had already been widely reported as much as a week ago.

Lagacé Dowson, a former Westmounter who now lives in Montreal, is hoping her high profile in the local English-speaking community will help send her to Ottawa. She has taken a leave of absence from her job as host of CBC's Radio Noon in order to focus her attention on the campaign.

NDP Deputy Leader Thomas Mulcair, whose victory over heavily favoured Liberal candidate Jocelyn Coulon in Outremont last year was considered a major breakthrough for the NDP in Quebec, was also in Westmount for Monday's announcement.

"It is very exciting to see that the people of Quebec are getting to know the NDP better," Layton stated last week in obvious reference to Mulcair's win and the momentum he hopes it will sustain in this province. "Quebecers are ready for something new, and they have begun to realize that we stand up for their interests and the issues that matter to them most."

The Westmount – Ville Marie by-election, which should be announced by Prime Minister Stephen Harper within the next two weeks, is expected to be held this fall.

With Lagacé Dowson's candidacy confirmed this week, the NDP is the last of the major parties to announce a candidate in the race to replace former Liberal MP Lucienne Robillard in Parliament. Guy Dufort (Conservative), Marc Garneau (Liberal), Claude Genest (Green Party) and Charles Larivée (Bloc Québécois) have all announced that they will be on the ballot.