As happened to his father former prime minister Pierre Elliott Trudeau in 1972, Justin Trudeau has lost his majority in the House of Commons and now faces the challenge of leading a minority government.

There are expectations that the New Democratic Party will have leverage to implement its own agenda in this new session of parliament, and the lessons of the past may prove to be instructive for NDP Leader Jagmeet Singh.

"I think the critical thing thing is to keep in mind the public interest and the interests of Canadians," said former NDP MP Libby Davies to Michael Enright, host of The Sunday Edition.

"This isn't just about doing some little deal behind closed doors. This is about representing what Canadians want to see on some of the key issues that, frankly, the Liberals have dragged their feet on for years, whether it's childcare or pharmacare."

Prime Minister Pierre Trudeau gives a speech on election night Oct. 30, 1972. He lost his majority that year. (Peter Bregg/Canadian Press)

Davies served as NDP house leader following the 2004, 2006 and 2008 federal elections, which all resulted in minority governments. She was in conversation with Ed Broadbent, who served as caucus leader for the NDP during the Liberal minority government of 1972 and later was party leader for 14 years.

"In his memoirs, and in personal conversation with Trudeau Sr. — I don't know if it's true of his son — he said that the period he enjoyed governing most was that minority government period," said Broadbent, "because, as he said, the pressure from the NDP he welcomed, to counter the right-wing pressure in his own caucus; and therefore he was able to do things as a Liberal prime minister that he otherwise would not have been able to do."

NDP MP Libby Davies asks a question during question period in the House of Commons on Parliament Hill in Ottawa on Thursday, May 2, 2013. (Sean Kilpatrick/Canadian Press)

​​​Broadbent said that at that time, the NDP successfully lobbied for election spending controls, improvements in pensions for Canadians and the creation of Petro-Canada.

During Paul Martin's minority government of 2004, NDP Leader Jack Layton convinced the Liberals to withdraw a corporate tax break and invest that money in transit, housing and pensions, said Davies.

Both she and Broadbent say a key factor in a minority situation is the personalities of the leaders.

"Pierre Trudeau seemed to be — to me, anyway — more open to progressive change than Justin has indicated. If you listen carefully to his [Justin Trudeau's] recent press conference after the election, he was willing to say, 'We'll listen to you,' namely all the other party leaders, 'if you agree with my agenda,'" said Broadbent.

"You know, he got the smallest vote in Canadian history — as a percentage — to form a government, since John A. Macdonald's time, but he did not indicate a sort of willingness to say, 'Well, maybe I have to change my agenda, not just move to persuade you on my agenda.'"

Broadbent also points out that the current session of parliament could have been more stable, had the Liberals kept their promise on electoral reform.

"We would have had 57 New Democrats elected and 116 Liberals," Broadbent said. "We would have had the possibility of a stable coalition of 173 seats, and that would have provided — in all regions of Canada with PR [proportional representation] — representation in all of the caucuses."

Trudeau has said he does not plan to form a coalition, formal or informal, with any one party.

NDP Leader Jagmeet Singh with Ed Broadbent, who served as leader for 14 years and was caucus chair during the 1972 minority government of Pierre Elliott Trudeau. They were touring the Ottawa farmers' market in October 2019. (The Canadian Press/Paul Chiasson)

"It's sort of like a three-layered chess game because we have to remember this is not just about the Liberals and the NDP. There are other political parties. There's the Bloc. There's the Conservatives. The opposition parties together can bring down the government, so that the dynamics of what's going on becomes very intense and can be very volatile," said Davies.

"I can remember some situations in minority parliaments where it was literally sometimes minute-by-minute in terms of what was going to happen, when a vote was emerging that was a confidence vote."

A confidence vote is one that can spark an election, if the House does not show confidence in the ruling party to govern. Confidence votes are taken for the Speech from the Throne, the federal budget, and any other matter the government deems to be a vote of confidence.

Broadbent points out that the Liberals likely will turn to the Conservatives for support on building the TransMountain Pipeline.

"He can get support for that. He won't get it from the NDP and he won't get it from the Bloc, but he could probably get it, and survive, from the Conservatives."

Click 'listen' above to hear the full interview.