The party was lead by Jack Layton since 2003 until his death in 2011, right before which he lead the party through the May 2nd 2011 federal election to a historical win that launched the NDP from third-party status to the Official Opposition for the first time ever, winning 103 seats in the Canadian House of Commons in the Parliament of Canada, making it the second-largest political party in Canada (they previously only held 32 seats and their previous highest record was 43 seats).
Three months after their historic win, on August 23rd, Jack Layton tragically passed away due to cancer. The party is currently lead by Thomas Mulcair (from the riding of Outremont, in Quebec). The NDP is also currently leading all public opinion polls, putting them in first place nationally (especially in the province of Quebec), ahead of the Conservative Party and the Liberal Party. 
The NDP is Canada's party of social-democracy, progressivism and environmentalism. The party is secular, pluralistic, promotes social equality and is a proponent of gay marriage, gender equality, protection of minorities, multiculturalism, regulation of the economy and the private and banking sectors in the name of the common good, maintaining Canada's social safety-net, welfare state and social programs to preserve the middle class and protect the poor, increasing social-assistance rates to be actually compatible with current living costs and standards of living, progressive taxation, lowering small business and low-to-middle-income taxes, ending the failed War on Drugs by legalizing and regulating (and taxing) marijuana and all recreational drugs and by implementing Harm Reduction methods rather than Prohibition.
They would also like to expand Canada's health care system to include dental and prescription drug coverage and to develop and expand social programs in general, like Old Age Security pensions (which were brought in by the NDP and are currently under attack by the Conservatives), pension indexing, and to create a national public daycare/childcare program, and a national public auto insurance program, and making (Un)Employmet Insurance (EI) more easily accessible, and raising the minimum wage to ensure that no one is paid anything less than a livable wage that realistically corresponds with the current cost-of-living, and of course making sure labour laws are fair and represent the needs of the workers and making sure that the law protects the trade unions to prevent corporations and other employers from exploiting anyone.
Speaking of corporations, many would be surprised to know that the corporate tax rate in Canada is not only ridiculously low, but it is actually the lowest in the entire Developed Western world- even lower than in the U.S-, so needless to day, the NDP feels this is hugely unfair and that huge tax cuts should not be given to those who need them the least and they advocate raising the corporate tax rate to make society fairer by having the tax burden shared fairly across society- and unlike what conservatives like to say, this would NOT make Canada "uncompetitive" because in social-democratic countries that have mixed economies, like Sweden and France, their MUCH fairer corporate tax rates have not only NOT made them uncompetitive, but they are actually the only economies in the world that, despite the economic disaster and recession that has hit laissez-faire unregulated economies like in the U.S, are actually booming and doing quite well, because those countries have not allowed the right-wing to demolish all of their social safety-nets, and not coincidentally, those countries have the highest standards of living and lowest poverty rates in the world), and many other typically social-democratic policies and programs .
Canada's single-payer universal health-care system was introduced to Canada by the NDP.
In order to understand what the NDP is all about, one must understand its predecessor and its history:
The NDP's predecessor is the Co-operative Coomonwealth Federation (CCF) , which itself was the result of a merger between previous parties. Although the current modern NDP is very much secular, the CCF began as part of the Christian Left and Social Gospel movement.
In 1944, in the Canadian province of Saskatchewan, the provincial CCF, lead by Tommy Douglas, swept to power with a huge majority government as a result of the 1944 provincial general election, and defeated the Saskatchewan Liberal Party government of Premier Gardiner. Tommy Douglas became the province's first CCF premier, and thus the first socialist government in North America was formed.
The CCF was in power for almost 20 years following that election, and they managed to form a majority government in every single election they won.
After assuming office, Douglas's government introduced Canada's first single-payer universal health-care program in North America (along with other major social-democratic reforms). Douglas's number one concern was the creation of medicare.
In the summer of 1962, Saskatchewan became the centre of a hard-fought struggle between the provincial government, the North American medical establishment, and the province's physicians, who brought things to a halt with the 1962 Saskatchewan Doctors' Strike. The doctors believed their best interests were not being met and feared a significant loss of income as well as government interference in medical care decisions even though Douglas agreed that his government would pay the going rate for service that doctors charged. The medical establishment claimed that Douglas would import foreign doctors to make his plan work and used racist images to try to scare the public.
Douglas is widely hailed as the father of Medicare, and took the opportunity to take his cause to the federal stage. Thus, in 1961, he retired from his position as Saskatchewan's premier and turned over the job to Woodrow Lloyd, taking leadership of the federal New Democratic Party.
The Saskatchewan program was finally launched by his successor, Woodrow Lloyd, in 1962. The success of the province's public health care program was not lost on the federal government. Another Saskatchewan politician, newly elected Prime Minister John Diefenbaker of the Conservative Party ...(yes, the CONSERVATIVE Party- THAT'S how popular the program was with the public, so much so, that even the Conservatives didn't dare to oppose it as it would have meant political suicide, and instead, decided to support it- although the national program didn't really come into its own until after the Conservatives were - thankfully- swept out of office federally, and the Liberal Party governments of Leaster Pearson and the social-democratic Pierre Trudeau came into power)... , decreed in 1958 that any province seeking to introduce a hospital plan would receive 50 cents on the dollar from the federal government.
In 1962, Diefenbaker appointed Justice Emmett Hall—also of Saskatchewan, a noted jurist and Supreme Court Justice—to Chair a Royal Commission on the national health system—the Royal Commission on Health Services. In 1964, Justice Hall recommended the nationwide adoption of Saskatchewan's model of public health insurance. In 1966, the Liberal minority government of Lester B. Pearson created such a program, with the federal government paying 50% of the costs and the provinces the other half. So, the adoption of health care across Canada ended up being the work of three men with diverse political ideals - Tommy Douglas, John Diefenbaker and Lester Pearson.
It should be noted that, although it was the Liberal government that implemented the program nationally, it wouldn't have been done had it not been for the NDP, because the Liberals were in a minority government situation with the NDP holding the balance of power. Thus, the NDP only agreed to support the minority government and not topple it if these social-democratic policies were implemented.
Influence on governmentEdit
Although the NDP has formed many successful provincial governments, it has not yet formed the federal government. Despite this, they have wielded a considerable amount of power in Canada's political history, especially in minority governments, by only agreeing to support the government on condition that they implement a huge variety of social-democratic programs and reforms. As a result, the overwhelming majority of Canada's progressive laws were all introduced by the NDP (especially during the 1972-74 minority Liberal government of Pierre Trudeau; as, although being a member of the Liberal Party, Trudeau was very much a social-democrat and agreed with the NDP's conditions the majority of the time).
Despite conservative propaganda attempting to scare the public by telling them that the NDP cannot handle an economy, the CCF/NDP governments of Tommy Douglas in Saskatchewan delivered 17 consecutive balanced budgets with surpluses.
Also, the results of four different scientific studies and research (which can easily be found on the Internet through Google) have shown that statistically, in all of Canada's history, the NDP has the best track record of balancing budgets. Federally, the party that had the worst economic record was the Conservative Party. In fact, since Canada was created, the Conservative Party has never been able to balance a federal budget and have run a huge deficit every single time they were in power. Since the NDP hasn't governed federally yet, between the Conservative Party and the Liberal Party, the Liberal Party was the only one that has ever delivered a balanced federal budget. Thus, this proves that, (since the Conservative Party is right-wing, the Liberal Party is mostly centrist and the NDP is solidly centre-left, and the studies concluded that it was the NDP that has the best economic record of all Canadian parties), the further to the left you go, the higher the level of economic and fiscal competence and number of balanced budgets.
In other words, the conservative-driven propaganda that society cannot afford to look after its citizens and that social-democracy isn't financially sustainable is the exact opposite of the truth.
In 1961, the CCF merged with The Canadian Labour Congress to form the current more moderate and social-democratic New Democratic Party of Canada (NDP). Tommy Douglas stepped down as Premier of Saskatchewan and from provincial politics to lead the newly created federal NDP instead.
In the 2011 federal election the NDP won a record 103 seats, becoming the Official Opposition for the first time in the party's history.
The party had a historic breakthrough in Quebec, where they won 59 out of 75 seats. This meant that a majority of the party's MPs now came from a province where they had previously only ever elected two candidates in the party's history, Thomas Mulcair and Phil Edmundston, and not concurrently), and had not been fully organized since 1990.
The NDP's success in Quebec was mirrored by the collapse of the Bloc Quebecois, which lost all but four of its 47 seats, and also the collapse of the Liberal Party (both in Quebec and nationally).
Jack Layton's performance on the French-language talk show "Tout le monde en parle" on April 3 was credited for improving his party's standing among francophone voters; it is the most widely-watched TV show in Quebec. He was also perceived to have performed well in the televised French-language party leaders' debate on April 13.
In reality, since Quebec is actually North America's most left-wing and progressive jurisdiction, the NDP surge there is not at all surprising and was just a matter of time. The only reason the NDP hadn't done well there before is that most of the voters voted for a party based on the issue of Quebec separatism (the separatist Bloc Quebecois party). To further prove this point, even the Bloc Quebecois is actually also a social-democratic party, but unfortunately it puts its agenda of Quebec separatism ahead of social-democracy.
Needless to say, the Cconservative Party has almost no presence in Quebec as Quebeckers are not conservatives, and the migration of the non-separatist (federalist) vote from the Liberal Party to the NDP made total sense as it was the natural path of evolution for the people of a province that is progressive by nature to go from voting for a centrist party (the Liberal Party) to a solidly centre-left party (the NDP).
Right wing governmentEdit
Unfortunately, the current government of Canada is formed by the Conservative Party, and its Prime Minister, Stephen Harper, has turned it into the most right-wing government in Canadian history. As a result, in the next Canadian federal election in 2015, Canada will need the centre-left NDP to win a majority federal government to undo all of the damage that the Conservative Harper government has already unleashed and will continue to unleash onto Canada. Voting for the Liberal Party will not be good enough anymore, for two reasons:
1) The Liberals have recently moved too much to the centre-right, and they aren't a social-democratic party.
2) Even if the Liberals were to move back to where they used to be on the political spectrum (centrist), and even though they are definitely less right-wing than the Conservatives, the current Conservative government is SO right-wing that Canada will need a solidly centre-left government (NDP government) to undo all the damage they have inflicted, and a centrist or centre-right Liberal government will just not do and not be enough (don't forget, "Liberal" in Canada does not mean social-democratic necessarily).
It is worth noting that the majority of the Canadian population is to the left of the Conservative Party, and that the majority of the population is progressive.
The current Conservative government was voted in by less than 38% of the Canadian voters, due to a flaw in Canada's first-past-the-post voting system which causes vote-splitting, resulting in a minority of the population being able to elect a majority government (a system which, if elected, the NDP would change immediately to a proportional representation system to protect Canada from such an undemocratic practice).
In other words, because the Reform Party and the Progressive Conservative Party (Canada's 2 right-wing parties) merged in 2003 to form the current Conservative Party, the right-wing vote goes to one party, while the more left vote goes to four different parties. This ends up splitting the vote on the left and allowing the undemocratic result of a minority of the population getting to vote in a majority government. Sixty-one percent of the electorate (the ACTUAL majority) voted AGAINST Stephen Harper's Conservative Party, yet he ended up winning a parliamentary majority government. This is proof that the winner-take-all nature of the first-past-the-post voting system is incompatible with Canada's multi-party political system.
The New Democratic party is a member of the Socialist International along with fellow social-democratic international parties such as Social Democratic Party of Germany, Labour Party (UK), and Parti Socialiste (Socialist Party of France).