The corn industry wants more corn in gasoline. Oil refiners want relief from the obligations that come with blending it. Donald Trump has identified a third necessary ingredient: Roger Marshall.

Roll Call reports that Trump told a Kansas rally he would support making year-round E15 permanent with Marshall in the Senate, but not if Democratic challenger Adam Hamilton wins. “I’m only doing it for him,” he said. Corn apparently needs a personal reference.

E15 contains 15 percent ethanol, rather than the usual 10 percent. Summer sales can currently depend on an EPA waiver. A permanent change would give corn producers a more dependable market. Trump already backed annual summer waivers in an executive order on the first day of his second term. The product has not changed. The political additive has.

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The actual negotiations are quite capable of producing a complicated bargain without him. A House bill would permit year-round E15 and replace annual exemptions for small refiners with permanent ones starting in 2028. But it would also count a parent company’s refineries together when deciding whether it is small. Owning several little refineries would become a less effective way of being a little refiner.

The Senate version offers permanent exemptions without that tighter definition. Oil interests disagree over the packages; some refiners warn the House approach could put more than 20 refineries out of business. These are disputes over who gets access to a market, who must blend renewable fuel and who gets excused. The concessions at least have something to do with the product.

It remains unclear whether a Marshall defeat would lead Trump to block next summer’s waivers or oppose the permanent legislation. Congress still has to pass a deal. Nobody should mistake the rally threat for an enacted fuel standard.

But the extra term is plain enough. A national industry negotiating year-round access has been asked to help secure six more years for one senator. The corn gets blended. Marshall gets renewed.