Republicans from farm-heavy states are not exactly prophets of free enterprise when it comes to their favorite industry. On agricultural policy, they are conservatives in the sense that they seek to conserve FDR’s system of farm socialism. Nowhere is this clearer than on ethanol.

The innocuous-sounding Renewable Fuel Standard (RFS), created by Congress in 2005, forces U.S. oil refineries to blend a specified volume of biofuels, primarily ethanol, into their products. Essentially, it requires that Americans put a certain amount of corn in their gas tanks for . . . reasons. Proponents argue that ethanol gives consumers greater choice and reduces their transportation costs. If true, it’s rather odd that ethanol needs a federal mandate to be sold, and that corn producers — not drivers........

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