In Donald Trump’s May 26th America First Energy Plan speech in Bismarck, North Dakota, he promised:

“We are going to rescind all of the job-destroying Obama executive actions, including the Climate Action Plan… We are going to save the coal industry… We’re going to cancel the Paris Climate Agreement and stop all payments of the United States tax dollars to U.N. global warming programs.”

Throughout the campaign, Trump has repeatedly debunked the climate scare, calling it “a hoax.” He labeled President Barack Obama’s assertion that climate change poses one of the greatest threats to the U.S. as “one of the dumbest things I’ve ever seen, or perhaps most naïve.”

Climate realists, those of us who do not support the hypothesis that greenhouse gas emissions from human activities are causing a climate crisis, have certainly been pleased. Here is someone with a good chance of becoming president apparently committed to ending the waste of hundreds of billions of dollars on the climate file.

Besides the direct impact a President Trump would have on climate and energy policy (if he keeps his promises), he would also have a very strong, positive effect on public opinion. In a paper entitled, “Shifting public opinion on climate change: an empirical assessment of factors influencing concern over climate change in the U.S.,” published in the journal Climatic Change, researchers at Drexel University, McGill University, and Ohio State University showed that the stated positions of politicians and other “elites” in society is the major factor driving public opinion. In support of this conclusion, leading climate skeptic Marc Morano of climatedepot.org said, “notice how the Czech Republic has high amounts of skepticism due to former Czech President, Václav Klaus, speaking out on the issue skeptically.”

But will Trump actually remain a climate realist if he becomes America’s chief executive officer? Or will he change his mind and instead support the politically correct position?

In 2009, Trump was on the other side of the debate, signing an open letter to President Barack Obama and Congress that stated:

“We support your effort to ensure meaningful and effective measures to control climate change, an immediate challenge facing the United States and the world today. Please don’t postpone the earth. If we fail to act now, it is scientifically irrefutable that there will be catastrophic and irreversible consequences for humanity and our planet…Please allow us, the United States of America, to serve in modeling the change necessary to protect humanity and our planet.”

The letter, endorsed by Trump and other prominent business leaders, as well as Trump’s children, Eric, Ivanka and Donald Jr., was published in the New York Times the day before the 2009 Copenhagen climate talks began.

There are more recent examples of Trump’s support for the climate scare. According to the New York Daily News, in 2014, the Donald J. Trump Foundation gave $5,000 to Protect Our Winters, an Olympic snowboarder’s climate change advocacy group. Time magazine reported on May 23, 2016 that the Trump International Hotel in Ireland cited “global warming and its effects” as a reason for its permit application to build a seawall beside its golf course at County Clare, Ireland, to prevent coastal erosion.

Republican insiders would not be surprised by all this. Many do not regard him as a consistent conservative, noting that he has frequently changed sides on contentious issues.

The Daily Caller points out that Trump was a registered Democrat from 2001 to 2008, and, according to the Washington Post, as of 2011, he had given 54 percent of his $1.3 million political contributions to Democrats, including Hillary Clinton, John Kerry, and the late Edward Kennedy. The Clinton Foundation website shows Trump listed as giving between $100,000 and $250,000 to the foundation.

This emphasis has changed in the past four years and PunditFact assert that, “since 2012, Trump has donated $463,450 to Republicans and just $3,500 to Democrats.”

Trump explains these donations as sensible business transactions. “When they call, I give. And you know what, when I need something from them two years later, three years later, I call them. They are there for me.”

In other words, over the years, Trump has been, generally speaking, a pragmatist. He does what works, given the environment in which he is operating. If, as president, he concludes that supporting the climate scare works best for his administration — and rest assured, climate activists will do everything in their power to make his climate skepticism as uncomfortable as possible — then he will almost certainly change sides again. So climate realists must pressure Trump to stay the course or they risk the sort of defection to alarmism that occurred with both presidents Bush.

Americans should look north for an illustration of what is likely to happen if climate realists do not hold Trump’s feet to the fire.

Before first winning a minority government in 2006, former Canadian Prime Minister Stephen Harper promised to get to the bottom of the climate change file. Neither he, nor most members of his Conservative Party of Canada, believed that greenhouse gas (GHG) emissions from human activities were causing a climate crisis. Emission reduction regulations were clearly not necessary, they said. In a 2002 fundraising letter for the now-defunct Canadian Alliance, Harper called the U.N. climate process “a socialist scheme to suck money out of wealth-producing nations.”

Yet despite being regarded as a genuine conservative, Harper changed sides on climate change soon after being elected. In an attempt to appease activists, he supported U.N. negotiations to ‘stop dangerous climate change.’ He made GHG reduction pledges Canada had no chance of keeping without destroying our economy, wasting billions of dollars in the process.

Party strategists decided that they had to play along with the climate scare until public opinion changed. Government cannot lead public opinion, they mistakenly assumed.

Harper could have made a major contribution to killing the climate scare in Canada, but climate realists did not pressure him to keep his pre-election promises. So he responded to those who did pressure him — climate activists.

Climate realists in the U.S. must strongly support Trump’s skepticism, providing him with the tools he needs to justify and maintain his current position. They need to convince his advisors to make full use of reports such as those of the Nongovernmental International Panel on Climate Change that demonstrate that much of what Clinton and Obama say about climate change is hopelessly misguided.

But, most important of all, climate realists must keep up the pressure to ensure Donald Trump does not follow the pathetic example set by Canada’s former Prime Minister and simply change sides after being elected. That would be a disaster for the U.S. economy, not to mention everyone else in the world who depends on a prosperous America for our freedom.

Tom Harris is Executive Director of the Ottawa, Canada-based International Climate Science Coalition.