Although Canada and the United States (U.S.) have a special responsibility to act on climate change given per capita greenhouse gas emissions among the highest in the world, both have repeatedly failed to meet their domestic emissions targets. Their failure ultimately reflects the formidable political challenge of transforming economies heavily reliant on fossil fuels, which prompts opposition from both emissions-intensive industries and voters resistant to higher energy prices. Efforts to mitigate climate change have been undertaken in fits and starts, with leadership flipping between the U.S. and Canada as center-left leaders have exercised institutional points of leverage available to them. However, Democratic presidents’ efforts have been stymied by Republican successors, while Canadian governments’ efforts have been undermined by concerns about competitiveness with the U.S. That challenge looms large once again as Canada has pledged to meet its target under the Paris Agreement despite Donald Trump’s reversal of the U.S. commitment.