Wisconsin shed 10% of its dairy farmers last year, according to data from the state's Department of Agriculture, Trade, and Consumer Protection.It marked the biggest drop in a single year, and underscored the negative impact of Trump's trade war in a state critical to his re-election bid.Last year, China slashed its purchases of American dairy products by 50%, helping to throw scores of farmers out of business.The business environment has particularly worsened for small farmers.Visit Business Insider's homepage for more stories.Wisconsin shed 10% of its dairy farmers last year, data from the state's Department of Agriculture, Trade, and Consumer Protection shows.It marked the biggest one-year drop on record, and underscored the negative impact of Trump's trade war on a swing state critical to his re-election bid.In 2019, Wisconsin lost 819 dairy farms, the department said, leaving 7,292 dairy farms in place. The state leads the nation in the number of farm bankruptcies, according to the American Farm Bureau."Producers have suffered without market controls to put the brakes on when demand is lower. The trade tariffs only added salt to the wound," said Julie Keown-Bomar, executive director of the Wisconsin Farmers Union, in an email.The group called for additional growth management to allow "for reasonable controls in the marketplace."After Trump launched his trade war against China and other friendly nations in 2018, China responded by slapping hundreds of billions of dollars worth of tariffs on American products.Last year, China slashed its purchases of American dairy products by 50%. Combined with falling milk prices, the trade war has thrown many farmers out of business. The economic environment has worsened considerably for small dairy farms in particular.The state's coveted 11 electoral votes went to Trump by 23,000 votes in 2016or less than one percentage pointa razor-thin margin that promises to make itanother key battleground in the 2020 election. Additional volatility could weaken his support among farmers, though their backing remains strong.Farmers have suffered significant business losses because of the trade war, resulting in a $28 billion bailout package that's double the amount the government forked over to Detroit automakers at the height of the recession a decade ago.Still, a greater share of that aid may be going to richer farmers. The Environmental Working Group, a nonprofit organization, said in a study released in November that wealthier farmers have drawn larger cash payments compared to poorer ones."If we don't begin to protect dairy producers with reasonable market mechanisms, only those large, corporate dairy farms that can cut their input costs to the shearest margins will be the ones to survive," Keown-Bomar said.Americans have also borne the brunt of Trump's tariffs. A paper released this week from the National Bureau of Economic Research found that consumers paid for "approximately 100 percent" of the tariffs in the form of increased prices.However, both China and the United States are set to sign a "phase one" agreement that would de-escalate the trade war on Wednesday.Join the conversation about this storyNOW WATCH: A big-money investor in juggernauts like Facebook and Netflix breaks down the '3rd wave' firms that are leading the next round of tech disruption Click here to read full news..