There’s a simple reason that ethanol is popular with politicians: money. Substituting corn ethanol for a large fraction of the gasoline we burn will mean sluicing gushers of cash from more populated states to politically powerful farm states. And a lot of that cash will wind up in the pockets of the big agribusinesses, like Archer Daniels Midland, that dominate ethanol processing—and whose fat checkbooks wield enormous influence in Washington.