Vancouver MP Joyce Murray has launched her bid for the leadership of the Liberal party.
Murray's announcement in Ottawa Monday kicks off a week in which at least two more candidates are expected to announce campaigns for the party's leadership.
Canada's first man in space, former astronaut and Quebec MP Marc Garneau, will tell a Montreal audience on Wednesday that he is challenging fellow MP Justin Trudeau for the leadership of the federal Liberal party.
The three sitting MPs along with former MP Martha Hall Findlay of Toronto are thought to make up the top tier of a field of candidates that could number in the double-digits.
Toronto lawyer George Takach, who has a campaign team that includes veteran Liberal organizer Mark Marissen, is also expected to announce his bid this week.
The 63-year-old Garneau flew three space shuttle missions before running the Canadian Space Agency.
After being defeated in his first run for office in 2006, Garneau was elected in the Montreal riding of Westmount-Ville-Marie in 2008 and was re-elected in 2011.
The former Navy combat engineer is expected to give up his duties as Liberal House leader.
Garneau, who also a former director of an energy company, was named his party's natural resources critic this week after David McGuinty resigned from that post on the heels of embarrassing his party with remarks that were aimed at Alberta Conservative MPs.
McGuinty's suggestion that Alberta Conservatives were too narrow-minded for federal office was followed up by Trudeau being forced to apologize for saying in a 2010 television interview that Canada was better off with Quebecers rather than Albertans running the country.
Both stumbles left Liberals reeling in Alberta ahead of a Monday byelection in Calgary-Centre where the party was thought to have a competitive chance of winning a seat in the city for the first time in decades.
Other declared candidates include Ottawa lawyer David Bertschi, Vancouver lawyer Alex Burton, Toronto lawyer and professor Deborah Coyne, retired Lt.-Col. Karen McCrimmon.
Other possible candidates include former Montreal MP Martin Cauchon, former president of the B.C. branch of the federal Liberal Party David Merner and economist Jonathan Mousley.
Liberal MPs Denis Coderre and Dominic LeBlanc, as well as interim leader Bob Rae, have said they won't run.