When Sen. Joni Ernst, R-Iowa, talks about what it is like to discuss trade with Trump administration officials, her description is similar to the way those same officials describe discussions with Chinese negotiators: It’s not clear what the other side wants or is willing to do, and things they thought the other side had previously agreed to do are subject to change.

Ernst, a 48-year-old former National Guard lieutenant colonel and a first-term senator from the agriculture-heavy state of Iowa, has backed President Trump on most issues but takes a skeptical view of the tariffs. She says they can be useful in bringing trade partners to the negotiating table, but they have to be temporary and must be removed once they have served that purpose so they don’t hurt the economy. Trump disagrees, she says, considering tariffs too potent and too useful to be dropped.