In his final rally before the Iowa caucuses, President Trump greeted Iowans Thursday by saying: "If we don't win, your farms are going to hell, I can tell you right now."

Flashback: The U.S.-China trade war was estimated to have cost farmers roughly $1.7 billion in losses last year, as the government paid $973 million in aid to Iowa farmers.

Background: As Trump hits the campaign trail before the caucuses — which is the first real test of candidates' appeal to voters — three 2020 Democratic contenders are sitting in the Senate impeachment trial for Trump.

Go deeper: Health care and abortion are the top issues being searched in Iowa