Liberal MP Justin Trudeau will announce his plan to run for the party's leadership tonight, with a rally scheduled for his riding in Montreal.

Radio-Canada last week broke the news of Trudeau's impending leadership bid, but Trudeau wouldn't confirm the story for reporters as he walked into the Liberal Party's weekly caucus meeting.

The rally is set for a community centre and is for Liberal supporters, according to a news release issued by a spokeswoman for Trudeau.

One campaign insider told The Canadian Press that tonight's rally will include a "meaty" speech, designed to demonstrate the youthful MP has  "a mature and thoughtful perspective on the country." It won't spell out any specific policy pronouncements but it will lay out Trudeau's "values, objectives and methods" of achieving them.

It will include Trudeau's blunt diagnosis of why the once-mighty Liberal party was reduced to rubble in the 2011 election: It lost touch with middle-class Canadians who used to be the party's bulwark. He'll offer his prescription for reconnecting with the middle class and rebuilding the party.

Trudeau's lack of experience as a critic on a major policy file is considered by some to be a weakness in his leadership bid. He has served as a critic for youth and immigration issues and been vocal about his environmental concerns. He's expected to draw on these areas to attract new Liberal support.

Cross-country tour this week

The Canadian Press reports Trudeau will set out across the country immediately after his launch, hitting Calgary, a Liberal wasteland since his late father Pierre Trudeau's hated National Energy Program, and Richmond, B.C., on Wednesday and a rally in Mississauga, Ont., on Thursday, hosted by former MPs Navdeep Bains and Omar Alghabra.

Among his key supporters is Gerald Butts, longtime friend and former head of policy for Ontario Premier Dalton McGuinty, and a raft of key organizers from policy-wonkish Gerard Kennedy's 2006 leadership bid, including campaign director Katie Telford, Bains and Alghabra.

Kennedy himself is still pondering whether he'll take a second run at becoming federal Liberal leader. He insisted Monday he won't be deterred by the fact that his old team seems to have moved, almost en masse, to Trudeau, who endorsed Kennedy in 2006.

The MP for Papineau, a working-class riding in Montreal, has been under enormous pressure to run for the leadership. The once-governing federal Liberals are consistently in third place in public opinion polls and lost more than half their seats, falling from 77 before the 2011 election to 34 (they're now at 35 after a New Democrat MP crossed the floor).

The Canadian Press reports Trudeau is expected to announce a raft of endorsements from Liberal MPs and senators within 10 days.

Trudeau had said he was worried about whether he would be able to be a good father if he were to become the Liberal leader. The father of two has some experience from the other side on that count. He was born about 3½ years after his father was first elected prime minister.

Race takes shape

A new Liberal leader will be chosen April 14. Bob Rae, the interim Liberal leader, has already announced he won't run.

While many have mused about running for the Liberal leadership in 2013, it's unclear how many will actually take the plunge, particularly now that Trudeau's confirmed his candidacy.

Toronto lawyer Deborah Coyne and Manitoba paramedic Shane Geschiere have announced they're interested in the leadership. Coyne is the mother of Justin Trudeau's half-sister, Sarah. Toronto lawyer George Takach, Ottawa lawyer David Bertschi and Vancouver lawyer Alex Burton have also said they may run.

MPs Marc Garneau, Dominic LeBlanc and Joyce Murray have said they're considering running for the party's leadership. Montreal MP Denis Coderre, who may also have designs on the Montreal mayoralty, has said he'll make an announcement in November.

Former MPs Martha Hall Findlay and Martin Cauchon are thought to be interested in running too.  The Canadian Press reports Ontario government economist Jonathan Mousley and David Merner, former president of the party's B.C. wing are also exploring bids.

With files from CBC News and The Canadian Press