At the same time that President Donald Trump visited Iowa on Thursday, anxious farm groups are fighting back and going after the controversial tariffs with a new multimillion-dollar ad campaign.The commercials take aim at Trump and his advisers for hurting farmers and manufacturers, the first real sign that an important part of Trump's base of support is turning against him.The commercial claims that "farmers, factory workers and rural communities are feeling the pain from President Trump's trade war.""Tariffs hurt the Heartland," said Nevada farmer Scott Henry, a new member of Washington, D.C.-based organization Farmers for Free Trade, which is behind the new ad. "It's hitting our pocketbooks with the nose dive that soybean prices have had."Henry supported Trump in the past, but said the tariffs are causing a 15 percent drop in the price of soybeans. Other agriculture prices are falling, too, which is why groups including the American Farm Bureau Federation and the National Pork Council are backing the four-month TV campaign."We're hoping to get the attention of not only the president, but also lawmakers to fully understand that these policies are hurting us," Henry said.The commercial also targets White House trade adviser Peter Navarro, who called the impact of the tariffs a "rounding error."Until a few weeks ago, Henry supported Trump, but Henry said, "At the end of the day, shutting markets off directly impacts our business far more than any of the gains we've experience so far."The TV ads are only part of the campaign. There will also be digital and print ads, as well as townhall events next month to target voters before the midterm elections.