For many centre-left Canadian voters, the New Democrats act as the conscience of Parliament. These voters don’t necessarily want the NDP to win power nationally. But they want enough New Democrats elected to nudge the government of the day in a more humane direction.

Such voters drive NDP stalwarts nuts. They point out that their party has successfully formed government in five provinces. Why, they ask, are Canadians so reluctant to see the New Democrats in power federally?

New Democrat MPs will tell you privately that they are sick of being the nation’s conscience and would like a real chance to put their ideas into practice.

But they will also admit that being seen as the party that represents Canada’s better angels is preferable to the alternative. Which is why they should be alarmed by the incremental but steady growth of the Greens.

In 2010, there were no elected Green politicians in Canada. Now there are Greens in four provincial legislatures and one in Ottawa.

In British Columbia, the Greens hold the balance of power. As I write this, voters in Prince Edward Island are deciding whether to take the plunge and elect Canada’s first Green government.

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In a world threatened by climate change, the Greens are by definition in a strong position to act as a moral force. The environment is their raison d’être.

By comparison, Justin Trudeau’s Liberals — with their emphasis on balance — seem wishy-washy, while Andrew Scheer’s anti-carbon-tax Conservatives appear positively antediluvian.

Federal Green Party leader Elizabeth May, meanwhile, projects an image of calm reason.

In large part, that’s because she doesn’t have to answer the hard questions levelled at those with a much better chance of becoming prime minister.

The Greens’ national platform, for instance, calls for lower personal income taxes, more social spending and balanced budgets — but without specifying how all three might be achieved at the same time.

A Green government would place tariffs on imports from countries that are not taxing carbon emissions. But the platform doesn’t explain how, in the real world of the WTO and trade agreements like NAFTA, it would manage this feat.

Politically, it doesn’t have to. As a purely moral force, May and her Greens are exempt from the usual questions such as: does all of this make sense?

She is exempt because, for now at least, not many expect her to become prime minister.

For a long time, this was the happy position the federal NDP occupied. It had plenty of good ideas. But with the exception of medicare, which was first instituted in NDP-governed Saskatchewan, it was never in a position where it could implement these good ideas.

For a brief moment in 2015, it looked as if this pattern might finally change. New Democrats, by then the official opposition, seemed poised to win that year’s federal election.

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Alas, the voters had something else in mind. Relegated once again to third-party status, the NDP returned to its traditional role as a moral voice in the Commons, decrying the Liberal government for its broken promises and offering up good ideas, such as universal pharmacare.

But is there room for two parties to act as the conscience of the Commons? More to the point, will disillusioned left-Liberal voters do as they have done in the past and gravitate to the NDP in order to express their disapproval of Prime Minister Justin Trudeau?

Or, in an era where climate concerns have become everyone’s concerns, will they cast their ballots for Elizabeth May’s Green Party in the hope that she can persuade whoever wins power in October to do something to halt the destruction of the planet?

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