It's still possible that Canada will emerge from 2019 with construction crews building a new pipeline from Alberta to the Pacific coast and a federal government committed to implementing a price on carbon and pursuing Canada's international commitment to emissions reductions.

If those things come to pass, it will be in no small part because of Rachel Notley. But however much influence she can exert now as leader of the opposition in Alberta, and beyond what her government did to change politics and public policy in her province, the ex-premier's national legacy is now in other hands — Justin Trudeau's, mostly.

If not for Alberta's first NDP premier, Trudeau likely would have had an even harder time crafting a national climate plan. If not for Notley, his government also might not own a pipeline right now. At the very least, he would have had a much harder time justifying his support for that pipeline's expansion.

For four years, Notley was at the centre of the stickiest debate facing this country: how (or whether) to respond to the challenge of climate change, to continue developing our natural resources, and to hold the country together in the process.

As it turned out, Notley's four years as premier were not enough to settle those questions. But she offered a key set of possible answers.

What Trudeau owes Rachel Notley

It was Notley who showed up to the first ministers' conference in November 2015 with the most important building block in what would become Trudeau's Pan-Canadian Framework on Clean Growth and Climate Change. Before flying to Ottawa, Notley announced a suite of measures to reduce Alberta's greenhouse gas emissions, including a new carbon tax and a cap on emissions from the oilsands.

It was some of the most significant climate policy ever put forward by a government in Canada. Among the provinces, Alberta was already the largest and fastest-growing source of emissions and the oilsands sector was an easy focus for anxiety about the future of the planet. Notley changed the terms of the debate by moving aggressively to take responsibility and challenge her province's reputation.

In doing so, she spared Trudeau from having to impose a solution on Alberta — a province that is particularly sensitive about its independence, particularly whenever someone named Trudeau is involved. And what Notley put forward became a model for the federal backstop now in place in Ontario, Saskatchewan, Manitoba and New Brunswick.

United Conservative Party leader Jason Kenney addresses supporters in Calgary Tuesday, April 16, 2019. (Jeff McIntosh/The Canadian Press)

But Notley also put a new, progressive face on the idea of building a new pipeline. And Trudeau leaned heavily on Notley's carbon levy and emissions cap to justify his government's decision to approve the Trans Mountain expansion.

This was Trudeau's grand bargain come to life. In the 2015 federal election campaign, he vowed to get Canadian resources to market and to implement a national price on carbon as a part of a comprehensive climate agenda. Each was a justifiable pursuit — but in pursuing them together, Trudeau could hope to achieve a durable and broad consensus.

And in a way, it worked. In 2016, just 41 per cent said the National Energy Board had made the right decision in approving Trans Mountain. By June 2018, 57 per cent of Canadians supported the project.

But the Federal Court of Appeal was another matter. Last fall, it found deficiencies in the federal approval process. In choosing to address those shortcomings, the Trudeau government had to delay further construction of the pipeline.

Could Trudeau use Trans Mountain as leverage?

Notley couldn't prevent that. She also couldn't prevent a drop in the market price for Alberta's oil. Nor, for that matter, could she change the fact that she was governing a province that naturally leans to the right.

There's a chance that construction of the Trans Mountain expansion will now be cleared to continue later this spring or summer, sometime shortly after Jason Kenney is sworn in as Alberta's 18th premier. (It's a little like how the Iran hostage crisis came to an end just as Ronald Reagan was sworn in as the American president in 1981.) But Kenney is also promising to make it harder for Trudeau to justify that pipeline — by promising to repeal the carbon tax and cancel plans for a cap on emissions from the oilsands.

Trudeau can use the federal backstop to fill the carbon pricing gap. The cap is trickier to replace. Might Trudeau use the pipeline (a pipeline Ottawa now owns, mind you) as leverage to negotiate a commitment to the cap? Could he? Could Trudeau rally the senior oil executives and companies who stood behind Notley in 2015 to call on Kenney to follow through now?

Rachel Notley might take solace in the fact that Jason Kenney campaigned on a platform that at least promised to do slightly more than the old Progressive Conservatives had been doing in 2015 — his carbon levy on major industrial emitters will be $20 per tonne, while the old PC policy set a price of $15 per tonne. Notley had raised it to $30. But perhaps this still counts as progress.

Notley's approach to climate and energy politics might still linger as a point of comparison with that of her successor. Watch, for example, to see whether public support for the Trans Mountain expansion is maintained with Kenney in the premier's office.

But significant forces are now aligned to pull apart the grand bargain that Notley and Trudeau struck. In British Columbia, John Horgan is challenging the pipeline, with the federal NDP's support. In Alberta, Saskatchewan and Ontario, conservative premiers are challenging the carbon price, with federal Conservative Leader Andrew Scheer cheering them on.

Trudeau is now on his own. And some of Notley's legacy depends on whether he succeeds.