President Trump risks losing a very important constituency among American farmers. Farmers and ranchers rely on trade and global markets, perhaps more than any other major part of our economy. The recent tariffs the president has suggested, especially those targeting China, and the likely resulting trade war, could upend the lives of American farmers as well as agriculture nationwide.

This isn’t the first time that trade politics and trade disputes have put farmers at the center of the debate. The president should learn from the example of Jimmy Carter when it comes to the impact of restrictive national policies impacting the politics of the heartland.

In 1980, President Carter ordered a grain embargo on the Soviet Union, which had invaded Afghanistan the prior years. This decision proved to be especially unpopular with US farmers whose grain sales to the Soviet Union were significant, and financial and political impact of the embargo on grain prices and related agriculture infrastructure lasted many years.

While Carter’s embargo and other actions were viewed by some in the foreign policy community as a credible response to the Soviet power grab, there is no question it had extremely negative consequences on agriculture and some other industries as well. It also had serious political consequences for Carter’s re-election campaign, and it certainly contributed to his loss to Ronald Reagan in the 1980 election. It also hastened the departure of a generation of farm state voters from the Democratic Party to the GOP.

American farmers, ranchers and agribusiness have been huge beneficiaries of global trade. Roughly one-third of all agriculture production is exported. The food and Agriculture sectors provide millions of US jobs, tens of billions of dollars to our economy, and food for the entire world. As the global economy has expanded over the past two decades, farmers and ranchers depend on foreign markets to stay economically viable. Producing for the domestic market only would produce catastrophic consequences for the agriculture sector.

Farmers aren't yet openly breaking with the president they overwhelmingly support. A senior leader representing farmers and the agriculture sector as a whole recently said: “We all have to admit that the style of this administration makes us nervous. But the point is, there are (trade) problems out there, and I think we’ve got an administration that’s determined to address some of those problems . . . (though) going after those problems comes at some high risk.” That was Chuck Conner, President and CEO of the National Council of Farmer Cooperatives, speaking at the Agri-Pulse Ag and Food Policy Summit last month.

We must acknowledge that the Chinese and others often engage in unfair and predatory trade practices, but the real question is how we calibrate our responses to make sure that we do not inflict tremendous harm on our own vital sectors. We risk damaging ourselves more from our response than from the action that precipitated trade retaliations.

All farmers understand the precarious position of agriculture in America. Agriculture has become so productive that it has become one of the key export markets for the United States. And when trade relations sour, agriculture becomes the first target of nations who wish to punish the US for their trade policy.

New trade policies of the Trump administration seem to be hitting farmers and ranchers very hard. Some farmers I talked to are comparing the impact of Trump’s trade war to a new embargo. Even though we live in the era of sound bites and attention deficit disorder, farmers have long memories. That’s what happens when you live your life by nature’s calendar.

Soybean, corn, cattle and pork producers will be the most impacted by potential Chinese reciprocal actions to President Trump’s tariff policy. These same farmers once supported the president but such a dramatic assault on their businesses and the very viability of their lifestyle could change the votes of farmers that went overwhelmingly for Trump in 2016.

There is still time to bring some reason and moderation to the president’s announcements, as Secretary of Agriculture Perdue has been a very positive force to date on NAFTA and other trade issues. It is in no one’s interest to foster conditions that threaten farmers and ranchers at this time of low commodity prices and reduced farm income.

About the author: Dan Glickman served as the U.S. Secretary of Agriculture from 1995 to 2001.