In CNN’s recent climate crisis town hall, fossil fuels—and the industry that produces them—were mentioned 153 times. Julián Castro committed to banning oil and gas drilling on public lands. Andew Yang supported a ban on offshore oil drilling. Kamala Harris promised to hold the fossil fuel industry accountable for its decades of climate deception. Bernie Sanders pledged to end fossil fuel subsidies and provide a just transition for displaced workers. Elizabeth Warren reiterated the importance of eliminating the corruptive political influence of fossil fuel companies.

This emerging focus on the supply of fossil fuels—compared to the usual fixation on consumer demand and greenhouse gas emissions—goes beyond debate rhetoric. Most candidates have now put forward climate plans that include a multitude of supply-focused policies. Even four years ago, it would have been unthinkable to see mainstream politicians outbidding one another on their commitments to phase out fossil fuel production and hold the industry legally, financially and morally accountable. (Bernie Sanders has been a notable exception that proves the rule.)

A focus on fossil fuel supply in climate politics is long overdue. “The largest, most extraordinary, and damaging misframing” in climate policy, climate communication specialist George Marshall observes, has been that the problem “could be defined entirely and exclusively as a problem of gases.” Never in the 25 years of international climate negotiations, including the Paris climate accord, has there “been a single proposal, debate or even position paper on limiting fossil fuel production.” Unlike every other issue—overfishing, illegal logging, drug smuggling, or smoking, say—when it comes to tackling climate change, U.S. politicians have rarely talked about keeping fossil fuels in the ground. Until now.

Climate change is a problem of coal, oil and gas supply as well as demand, for several reasons. First, fossil fuels are responsible for over 76 percent of greenhouse gas emissions. As scientists have been warning for years, holding global warming well below the Paris Agreement’s 2 degree Celsius limit means that we simply cannot burn the majority of existing fossil fuel reserves—those already on the books of investor- and state-owned companies.

Yet the carbon majors continue to spend hundreds of billions of dollars every year searching for new fossil fuels that the world can never afford to burn. Meanwhile, many countries continue to support fossil fuel production despite stated ambitions to cut greenhouse gas emissions, creating a “production gap” that widens the “emissions gap” between current climate pledges and the Paris Agreement goals. This, in turn, could lead to what economists and financial experts call stranded fossil fuel assets: a multitrillion dollar “carbon bubble” waiting to burst. No wonder $11 trillion of global assets have already been divested from fossil fuels.

Moreover, as a growing number of scholars, policymakers and activists have observed, the fossil fuel industry’s stranglehold on politics is a fundamental bottleneck to serious climate action. Fossil fuel interests have spent—and continue to spend—hundreds of millions of dollars deliberately misleading the public and stifling policy through disinformation and lobbying.

These are all reasons why fossil fuels must take center stage in any serious climate plan. It’s also worth remembering—and probably helpful for politicians to remind voters—that besides a collapsing climate, the extraction of coal, oil, and gas is associated with air and water pollution, worker safety hazards, social and environmental injustices and habitat destruction.

It is no accident that fossil fuels are becoming a political pariah. Many candidates have undoubtedly taken inspiration from climate champion Jay Inslee’s comprehensive and supply-centric plan. Yet the shift in political momentum is also the product of longer-term forces.

First, it is the result of activism. From fossil fuel divestment, to “blockadia” (civil disobedience targeting fossil fuel infrastructure), to the #NoFossilFuelMoneyPledge that candidates are being held to by the Sunrise Movement, to shareholders demanding that companies demonstrate that they comply with the Paris Agreement (and exposing that they don’t), grassroots movements have worked to reframe the climate narrative as not just a technocratic problem about greenhouse gases, but also a moral problem about fossil fuels.

Second, grassroots voices have been complemented by economic warnings—and divestment decisions—from many of the world’s foremost investors and finance experts. Recently, for example, market analysts reported that in the past year alone, “all major oil and gas companies have approved projects that are not consistent with the Paris goals.” More than 90 percent of ExxonMobil’s potential spending on new projects through 2030 would be stranded in a low-carbon world.

Third is the underlying science and policy. From climate scientists showing that existing fossil fuel reserves already exceed the global carbon budget, to political scientists suggesting that smart climate action requires addressing both demand and supply, to the academics and NGOs carrying these messages to decision-makers, a small but dedicated group of researchers are helping to rewrite how we approach the climate crisis.

Finally, investigative journalists and scholars have begun to uncover skeletons in the fossil fuel industry’s closet, informing dozens of lawsuits seeking to hold companies accountable for not just climate damages, but their denial and delay too. Most damning have been discoveries of internal memos showing that the fossil fuel industry has known about the potential global warming dangers of its products for 60 years. CNN’s Kevin Anderson cited research by one of us when he asked Joe Biden: “Will you hold fossil fuel corporations and executives who have lied to the public accountable?”

The U.S. is currently the world’s top oil and gas producer, and one of the leading laggards on climate action under the Trump administration’s pro–fossil fuel agenda. Yet by bringing fossil fuels into the picture, Democrats may be onto a winning climate narrative—for the election and Green New Deal legislation: Building a healthier, safer, thriving clean energy economy (which Americans love) by making fossil fuel polluters (which Americans love less) pay for their damages, denial and delay.

Supply-focused policies could come in many forms, including setting explicit climate targets based on tons of oil, coal and gas extracted; ending all fossil fuel production subsidies; banning or restricting production; suing the fossil fuel industry for the damages and deaths attributable to its products and obstructionism; rejecting all fossil fuel campaign contributions; clamping down on the fossil fuel industry’s lobbying and its revolving door with government; and creating just economic opportunities for fossil fuel–dependent communities.

We think that politicians who truly understand what it takes to tackle the climate crisis will not shy away from including supply-focused measures in their policy tool kit.

The views expressed in this commentary belong to the authors.