“Follow the money” is a basic rule of American politics. Find out who funds a given candidate’s campaign—and, equally as important, who isn’t funding it—and you can make a pretty good guess as to which interests and policies the candidate will support or oppose once in office. As the 2016 presidential campaign heats up, voters deserve to know where candidates stand on the challenge of our time: confronting the growing danger of climate change. In recent months, scores of governments, universities, companies, and pension funds around the world have begun to divest from oil, gas, and coal companies whose products are driving climate change and whose lobbying and public relations have delayed action and blocked solutions. Now it’s time for the politicians who wish to lead the United States to stand up and be counted: Will they too cut their financial ties with fossil-fuel companies by pledging not to solicit or accept campaign contributions from them for the 2016 election?

Just as fewer politicians welcome campaign contributions from tobacco companies, whose products cause cancer, so politicians should now shun contributions from fossil-fuel companies, whose products are overheating the planet and unleashing deadly and destructive droughts, storms, heat waves, wildfires, and other extreme weather. Tobacco executives knew perfectly well that their products were addictive and that millions of people would die if they kept smoking them. Likewise, fossil-fuel executives have known for decades that their products are the main drivers of climate change, and that the effects would be catastrophic if humanity kept burning more of them.

The International Energy Agency has echoed the scientific finding that 80 percent of the earth’s remaining fossil fuels must be left in the ground if humanity is to have a fair chance of limiting global warming to 2 degrees Celsius, the internationally agreed-upon target. This two-degree limit, scientists say, is by no means safe; rather, it is the threshold between “dangerous” and “extremely dangerous” climate change. The global insurance industry, unlike Big Oil and Big Coal, is heeding such warnings. “If we think we can live in a world where temperatures would have increased by more than 2 degrees Celsius, we’re just fooling ourselves,” said Henri de Castries, the chief executive of AXA, France’s largest insurance company.

Nevertheless, virtually every major fossil-fuel company insists that its business plan trumps the need to preserve a livable planet for future generations, not to mention the global poor who already bear the brunt of climate change. Thus, Shell—with the blessing of the Obama administration—races to drill for oil in a melting Arctic, while ExxonMobil declares that the global production and consumption of oil and gas must increase for decades to come. But not to worry, declares Rex Tillerson, ExxonMobil’s CEO: Humanity can “adapt” to unprecedented temperature increases by moving “crop production areas around”—as if the Midwest’s rich soils can simply be dug up and moved to Canada.

Meanwhile, the carbon barons employ their vast wealth and the political and media influence it buys to maintain the status quo, confusing the public with disinformation and cajoling or intimidating the people’s elected representatives into refusing a safer course. In the 2012 elections alone, the oil and gas industry contributed at least $76 million to presidential and congressional candidates, according to the Center for Responsive Politics; the coal industry spent an additional $15 million.

That $91 million sounds like a lot of money to the average person, but it’s pocket change to multibillion-dollar fossil-fuel companies—and they reap a stupendous return on their investment. For decades, such campaign contributions have bought the allegiance (or submission) of Democrats and Republicans alike. The resulting compliance on the part of Congress and the White House has led the federal government to increase its subsidies for fossil-fuel production—paid for with our tax dollars—to $18.5 billion a year in 2012, according to the NGO Oil Change International, while restricting solar, wind, energy efficiency, and other climate-friendly alternatives to a relative pittance. No less important, Washington has declined to put a price on the fossil-fuel industry’s carbon pollution. Instead, it’s the public that pays the full cost of coal production in the form of at least 13,000 excess deaths and tens of thousands of heart attacks and asthma attacks every year. This additional favor to fossil-fuel production boosts the value of the total public subsidy to a staggering $700 billion a year, according to the International Monetary Fund.

With climate change already pushing our civilization toward what Pope Francis has called “unprecedented destruction of the ecosystem,” policies that encourage more fossil-fuel production qualify as not just expensive, but suicidal. They must be reversed as quickly as possible, but that won’t happen as long as ExxonMobil and its corporate brethren continue to exercise a de facto veto over US energy and climate policy.

To break the carbon barons’ grip over America’s response to this crisis, The Nation calls upon all 2016 presidential and congressional candidates to make and honor the following pledge: In the name of protecting our country and the world from the growing dangers of climate change, I will neither solicit nor accept campaign contributions from any oil, gas, or coal company.

The Nation asked each of the major declared presidential candidates in the Democratic, Republican, and Green parties if he or she would make and honor this pledge. So far, two have responded affirmatively: Democratic candidate Bernie Sanders and Green candidate Jill Stein. Two other Democratic candidates, Martin O’Malley and Lincoln Chafee, said they supported strong climate action but would not sign the pledge. [UPDATE: On July 7, Martin O’Malley’s campaign contacted The Nation to let us know that the governor has agreed to the pledge.] Hillary Clinton, like the 14 Republican candidates contacted, did not reply.

The Nation looks forward to further coverage of this issue as the 2016 campaign unfolds. After all, candidates can change their minds—especially when enough public pressure is brought to bear.