Fifty years ago at the NDP's founding convention, Tommy Douglas said he believed the newly-formed party would one day form the government of Canada.

It's not quite there, but the NDP is as close as it's ever been. At this weekend's policy convention in Vancouver, the Official Opposition party will throw itself a 50th birthday bash that will include a retrospective look at its evolution.

The party has come a long way from when it was formed in 1961 and it has seen its share of ups and downs.

The New Democratic Party was born through the unification of the Co-operative Commonwealth Federation and the Canadian Labour Congress. Douglas, the legendary political figure best known as the architect of Canadian medicare, was its first leader.

He was chosen at that historic 1961 convention in Ottawa over Hazen Argue, a fellow politician from Saskatchewan. Argue, who had been a CCF MP, ditched the NDP after he lost the leadership to Douglas by more than 1,000 votes. He joined the Liberal Party and was later made a senator.

"This is not the time to argue, you'll pardon me using that word " Douglas said during his pitch to convention delegates, drawing a laugh from the crowd. "This is not the time to argue about right wings or left wings. This is the time to unite all our forces for the task which lies before us — the task of creating a society which will make the wealth production of Canada available to all who labour with hand and brain."

Douglas went on to talk about leadership and the importance of unity within a party in order for it to achieve success.

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Former and current NDP leaders Ed Broadbent and Jack Layton are in Vancouver this weekend where the NDP is celebrating its 50th anniversary. (Canadian Press)

Today's NDP leader, Jack Layton, and Douglas have a lot in common, according to another former party leader, Ed Broadbent.

He led the party from 1975 to 1989, and in 1988 had brought the NDP to its highest seat count in its history — 43. That record has now been shattered by Layton who has a caucus of 103 MPs.

Quebec's role in NDP history

The NDP's success on May 2 was largely due to the "orange wave" that swept through Quebec. The party went from one to 59 seats in the province.

A breakthrough in Quebec is what eluded Broadbent and was the reason he resigned as leader, he told CBC News in a recent interview.

"The wind went out of my sails personally, I really saw that as a big setback," he said. "I left over Quebec essentially in 1988 — we didn't get the breakthrough."

He describes the historic election result in May as a "glorious moment" and while the party is now far different in its composition than when Broadbent was in the caucus, he says it hasn't strayed from its roots.

"I don't think the party has changed ... the issues have changed," Broadbent said, explaining that the party adapts to whatever issues are current at the time.

Back in the 1970s and '80s, feminism was a big issue, he said as an example, whereas now Canadians are concerned with health care and pension security.

"I don't think there's a shred of evidence that would say it's changed its core values of equality, liberty, solidarity, what it believes in," he said.

Broadbent and Layton have both enjoyed incredibly high public opinion approval ratings, but their personal popularity hasn't always translated into success for the party. Until now, the NDP had been stuck in the corners of the House of Commons, never on the government or opposition benches.

Layton, a Toronto city councillor before he came on the federal scene, was determined to change that. He was elected leader in 2003, and has been steadily growing the NDP's vote share in every election since then. He now has the keys to Stornoway, the residence for the Official Opposition leader, and he's gunning for 24 Sussex Dr., where Prime Minister Stephen Harper now lives.

NDP's ups and downs

The party is riding a wave of optimism and celebration right now, but it hasn't always enjoyed such jubilant times. In the early 1970s it faced a crisis of division when a subgroup formed within the party, called the Waffle Group. It called for the protection of national unions as opposed to international ones and mounted a campaign for less corporate American ownership in Canada. It threatened to disrupt the party's momentum and in 1972, it was disbanded.

 In 1993, Broadbent's successor, Audrey McLaughlin, failed to keep the party's seat count in the double digits and the NDP dropped to just nine seats after the 1993 election.

McLaughlin, the first woman to lead a Canadian political party at the federal level, passed the torch on to another woman, Alexa McDonough. She set about to rebuild the party from its setback and slowly but surely it gained ground again.

Though the NDP had been the fourth party in the House of Commons for years, its members say they have been able to wield great influence. They often point to the deal Layton struck with then-Liberal prime minister Paul Martin in 2005 as an example. Layton supported the minority Liberal government in a crucial budget vote in exchange for amendments to the budget.

The following year, he helped bring Martin's government down when the NDP supported a motion of non-confidence moved by Harper and the Conservatives.

The NDP has worked hard over the last several years to widen its appeal to Canadians and to edge out the Liberals as the main alternative party to the governing Conservatives. It has celebrated isolated victories along the way, such as when current Deputy Leader Thomas Mulcair stole Montreal's Outremont seat away from the Liberals. When Linda Duncan captured the only non-Conservative seat in Alberta in 2008, it was also cause for celebration. She was only the second NDP MP to ever be elected in the Tory stronghold.

Brad Lavigne, the party's national director who is now leaving that post to become Layton's right-hand man, says the NDP's founding members would be proud of how far the party has come.

"If you take a look at the architects of our founding back in 1961, they spoke about the day where we'd be in a position to be the government-in-waiting," he said this past week. "And I'm sure they're smiling down this weekend on New Democrats in Vancouver."

At its founding convention, NDP delegates sang Solidarity Forever. At this year's convention, the crowd is likely to sing Happy Birthday, loudly and proudly.