Liberal MP and former astronaut Marc Garneau announced Wednesday morning he's "throwing his hat in the ring" and entering the Liberal leadership race.

At a press conference in Montreal, Garneau said his goal is to restore integrity and principle to politics in Canada.

Under Prime Minister Stephen Harper, he said, " We have an angry, divisive, intolerant government," that practices the politics of exclusion. The government, he said, wraps itself in the flag, but fails veterans. It ignores scientific evidence, but, he said, he believes in a knowledge-based economy.

To those who think Liberals might be crushed between the Conservatives and the NDP, he said, "Never!" The Liberals are not the NDP, he said: "We don't believe government can do everything."

Speaking to reporters after his announcement, Garneau said the results in Calgary Centre for Liberal candidate Harvey Locke were very encouraging, and indicate the Liberals are once again a force in the West, dodging a question about the vote split in that riding between the three opposition candidates.

Asked again about the possibility of co-operation with the NDP, Garneau said he would not endorse a policy advanced by another leadership candidate, MP Joyce Murray, on run-off nominations. If he becomes leader, Garneau said, there will be 338 Liberals running in the next election, and as far as he'll go when it comes to alliances with the NDP will be working with the party in the House of Commons.

At his second press conference of the day in Ottawa Wednesday, he confirmed that there is no form of electoral co-operation that he would consider, and that he believes that Canadians should have a choice when they go to the ballot box.

Another celebrity

Garneau adds another kind of celebrity to a race that's been dominated by Trudeau, who is often referred to as the "rock star candidate."

When someone tweeted to ask whether Garneau would be "window dressing" in a contest where he will run against Justin Trudeau, he answered, "Do you really think I would take on a huge personal commitment to be window dressing?"

What other leadership contender has two high schools named after him, as Garneau does? Who else was once asked by the Montreal Alouettes to try out for their team, as he revealed on Twitter during the Grey Cup furor.

As for his fame for being a literal space cadet, Garneau said he's at ease with it, and then pointed out that when he applied to be an astronaut, there were 4,000 applicants. " I ended up number 1. I like taking on challenges, and I'm taking on this challenge, and I intend to win."

Garneau, born in Quebec City and a Royal Military College graduate, became a naval officer after getting his doctorate in engineering. In the mid-80s he became one of six Canadian astronauts and flew his first shuttle mission in 1984. His biography on his website says he's logged 644 hours in space.

In 2001, he became head of the Canadian Space Agency and left in 2005 to enter politics. He lost his first election in 2006, but in 2008 won the riding of Westmount-Ville-Marie. He is the party's critic for science, industry and technology. In his political career, he has championed the idea of a commissioner for children and young people.

To focus on his campaign, Garneau has stepped down from his role as Liberal House Leader. New Brunswick MP Dominic LeBlanc was named as his replacement by interim leader Bob Rae.

Garneau becomes the third sitting MP to enter the race, after Justin Trudeau and B.C. MP Joyce Murray.

Garneau has 'intellectual heft'

One supporter says he is attracted to Garneau because of his "intellectual heft." A Liberal insider says that if Trudeau falls flat on his face, then Garneau will be there as a solid, credible candidate, and a household name to boot.

Liberal MP Marc Garneau hugs his mother Jean after announcing his candidacy for the Liberal party leadership Wednesday, November 28, 2012 in Montreal. (Paul Chiasson/Canadian Press)

At 63, Garneau qualifies as an early boomer, a member of a political age-cohort that ranges from Bill and Hillary Clinton, Mitt Romney, Bob Rae and a number of his seatmates on the Liberal bench.

There is a sense of the headiness of what it was like coming of age in the 60s as he relates how he crossed the Atlantic in an 18-metre yacht with 12 others in 1969, the same year, he notes, as Woodstock and the moon landing.

His 8000 Twitter followers don't compare to Trudeau's nearly 170,000, but nothing humanizes him more than some of his tweets, as he obligingly answers questions about life in space. Is there a special space toilet, how does the shuttle's vacuum cleaner work when the shuttle's flying in a vacuum, is there a Velcro strip inside the helmet to aid in nose-scratching? (Answers: yes, it just does, and no).

'Liberals don't have a natural entitlement to govern'

The Liberals don't have a natural entitlement to govern Canada, he said, stressing that the right must be earned.

The economy will be his number one priority, Garneau said, saying that under Stephen Harper Canadians have almost become hewers of wood and drawers of water gain, due to the reliance on the bounties of natural resources.

Investment should be poured into start-ups, he said, and taxes should be lowered for everyone, not just special interest.

Canada's global reputation must be restored, Garneau said, adding that "it's not rocket science, and I know something about rocket science."

At the Canadian Space Agency where he was president for four years, he said he had the experience of managing a budget of millions of dollars, and that he deserves to be known for more than just being one of Canada's first astronauts.

Garneau revealed that he has deposited the first instalment of the non-refundable $75,000 entry fee for the Liberal leadership, adding that maybe the field won't be quite so crowded as it presently appears to be, since he is only the third candidate to put down money (along with Trudeau and Toronto public policy consultant Deborah Coyne.)

The other candidates who have declared their leadership bid or their interest are former MP Martha Hall Findlay, Ottawa lawyer David Bertschi, Vancouver lawyer Alex Burton, retired air force colonel Karen McCrimmon, senior government economist Jonathan Mousley, B.C lawyer David Merner and Toronto lawyer George Takach.