Prolly related to ethanol subsidies & crop insurance issues. Farmer's hands are are tied in myriad ways. When it is time to plant & or harvest they have to make decisions that can make or break them for that year/season. Grassley is a farmer & so are his most ardent supporters. IMO right or wrong he opposes these tariffs because he believes it will hurt Iowa's farmers.
In '95 I had issues w / my GI bill related to Gov shutdown under Clinton. I tried everything I could thru my college & got no kinda help. I contacted Grassley & he & his staff had it fixed in 2 weeks. For Gov work was @ lightspeed. Am willing to cut him much slack.