One farmer addressed exactly that. Kelly Nieuwenhuis, a corn and soybean farmer near Primghar in northwest Iowa who also sits on the Iowa Corn Promotion Board and is president of the Siouxland Energy board, called the EPA’s handling of the RFS "pretty disgusting." And he said it could prove costly to Trump.

"My personal perspective is President Trump has lost a lot of support, pretty much everyone I talk to that’s involved in agriculture and the biofuels industry, really lost trust and are really frustrated," Nieuwenhuis said.

That’s a comment that cannot be overemphasized. For months the question has been whether Trump’s policies on trade and ethanol, which have contributed to lower commodity prices, would come home to roost. The answer remains subjective, but the comments from that press conference suggest the Trump re-election campaign team should be at least a little concerned.

Monte Shaw, executive director of the Iowa Renewable Fuels Association, said there is still time for Trump to make a save here. Shaw said he views this is purely an EPA proposal, and if Trump nixes the proposal and insists on a previous pledge his staff made to Iowa renewable fuels leaders, then Trump will emerge from the episode largely unscathed.