When Canadian Prime Minister Justin Trudeau came to power in 2015, he promised a grand bargain: his Liberal government would fight climate change with a carbon tax, but would also get Canadian oil to new markets in Asia. One would buy the social license for the other.

As bargains go, it didn’t have the desired effect. Provincial governments took Ottawa to court over the federal carbon tax, and the Liberals have yet to get a new pipeline built to the Pacific West Coast.

It’s now the defining challenge of Trudeau’s nascent second term as prime minister – and it’s getting harder. He has to set Canada on track to exceed its emissions target under the Paris Agreement, even as he builds a new pipeline out of the Alberta oil sands. He has to prove that his government, which has made fighting climate change central to its brand, can make good on its promises without making more enemies.

It’s a far cry from the landscape south of the border, where since 2016, President Donald Trump has withdrawn the United States from the Paris Agreement and has sued California for its cap-and-trade deal with Quebec. In Canada, voters are increasingly demanding that their leaders have a clear plan to cut emissions. Even Canada’s Conservative party, currently in the throes of a leadership race, is grappling with how to win voters’ trust on climate change.

But there’s no easy path forward for Trudeau, who faces tough decisions about the future of the country’s oil-and-gas industry and concerns from Western Canada that he wants to shut it down. When the Liberals were reelected last October, they’d lost all their seats in oil-rich Alberta and Saskatchewan, a sign of deepening regional divisions. Trudeau now needs to figure out how much, and how quickly, Canadians actually want climate action.

As Canada’s Parliament resumed last week, the challenges facing the Liberals on climate change coalesced into a single question about a proposed oil-sands mine in northern Alberta. By the end of this month, Trudeau’s cabinet will have to decide whether to approve Teck Resources’ $20-billion Frontier mine, a massive, polarizing project with a big environmental footprint that could produce up to 260,000 barrels of oil a day.

The decision, coming as it does at the start of Trudeau’s second term, will be taken as a sign of the Liberals’ true colors on climate change and resource development. If they don’t approve it, they’ll be accused of trying to phase out the oil sands. If they do, they’ll be accused of not being serious about reducing emissions, especially after their 2018 decision to buy a controversial oil pipeline project that’s currently under construction.

The Liberals would likely prefer to take the spotlight off the Teck decision. “My message, I think to everybody, is we need to look at this project and make a decision on the merits,” Environment Minister Jonathan Wilkinson told POLITICO. “But I’m not sure that it’s in any way a referendum on either the government’s position on climate change or our position on natural resource development.”

Empirically, it may not matter whether the Liberals approve the project. The company hasn’t made a final investment decision on the mine, and without higher oil prices, its future is very unclear. “There’s no sense in which this is a project that is likely to be built,” said Andrew Leach, an energy and environmental economist at the University of Alberta. Even if it were, he said, the four megatonnes of greenhouse gases it would produce annually are probably not going to determine whether or not Canada meets its emissions targets.

“There is kind of an industry of trying to make this into a litmus test,” a government source said. “I’m not sure that it actually is.”

Still, the decision has taken on symbolic weight. “Saying that they’re committed to climate leadership but then doing the opposite will not make us win the fight against climate change,” said Laurel Collins, environment critic for Canada’s left-of-center New Democratic Party. “And we’re running out of time.”

CBC News reported last weekend, citing anonymous sources, that the Liberal cabinet is leaning toward approving the project with conditions, including that Alberta get on track to becoming carbon-neutral by 2050. A second government source told POLITICO those claims are overstated, and it’s not the case that cabinet is leaning toward that plan.

But Wilkinson has repeatedly said the government must consider whether the mine is consistent with Canada’s climate goals. “I’m not going to say that it’s necessarily inconsistent, but certainly one would have to find ways to make it consistent,” he said. The first Liberal source told POLITICO the project could coexist with serious action on climate change if, for example, the company had a plan to become carbon-neutral and if Alberta committed to enforcing its existing cap on emissions.

Arguably, though, Trudeau’s bigger problem is that Canada is not on track to achieve its own goals, with or without the Frontier mine. Despite the federal carbon tax, which came into effect last spring in provinces that didn’t have their own, Canada is still projected to miss its 2030 emissions target under the Paris Agreement by 77 megatonnes, and doesn’t have a clear plan to make up the gap. Undaunted, Trudeau upped the ante during the last election campaign, promising to set Canada on a path to achieving net-zero emissions by 2050. Wilkinson has also said the government will come up with a new, more ambitious 2030 target sometime this year.

Those promises likely helped earn the Liberals enough center-left votes to keep them in power, but now they have to deliver where governments before them have failed — Canada has never met any of its emissions targets. “If you can be the government that basically lays the pathway and makes it pretty hard for us to miss our Paris targets, that’s a massive win,” Leach said.

It will take a deft hand. The Liberals passed the carbon tax in the face of intense opposition from provincial Conservative governments, and won’t say whether they’ll continue to increase it after 2022. Their focus now is on less visible ways of cutting emissions — increasing the renewable content in fuels, for example, and planting two billion trees. For all that Canadians want to hit the Paris target, many don’t want to feel they’re paying for it.

Still, the Liberals feel they have some room for movement. In the last election, two-thirds of Canadians voted for parties that support a carbon price. The Liberals were reduced to a minority government and will need opposition support to survive, but they will likely find allies on climate action in the New Democrats and the Bloc Québécois.

The Conservatives, meanwhile, have to find a path forward after an election in which the Liberals successfully painted them as not caring about the environment. “One of the things that caused us not to win in the last election was people didn’t think our climate plan was credible,” said Ontario MP Marilyn Gladu, a candidate in the race to replace leader Andrew Scheer.

The main contenders in the Conservative leadership race have all said they would scrap the federal carbon tax, which is deeply unpopular among their base. “With Peter MacKay as Prime Minister, there will be no carbon tax,” the frontrunner declared Thursday on Twitter. But they must find a way to sell a meaningful alternative, said Conservative strategist Jamie Ellerton. “They are generally perceived by the public to be anti-action on climate change,” he said. Until that shifts, Ellerton believes, Trudeau’s Liberals will remain the champions of climate action.

On the same day Trump attacked “the perennial prophets of doom and their predictions of apocalypse” at the World Economic Forum in Davos last month, Trudeau emerged from a cabinet retreat in Winnipeg and promised, again, to do more to fight climate change. “In this mandate, we’re really going to see what emerges as their view of what their legacy should be,” said Tim Gray, executive director of advocacy group Environmental Defence.

But climate change isn’t an easy issue on which to stake a government’s legacy, with results measured over decades, not election cycles. “If all of it ended today, I think we have the facts on our side to say this government did more on climate change than any other government before it,” said the first Liberal source. “But it’s not a competition between us and previous governments. … It’s the challenge of our time.”