So, why do refiners put ethanol in your gasoline? Because the federal government requires it. The federal ethanol mandate created by President George W. Bush (officially the Renewable Fuel Standard) was a sop to the ethanol lobby, which wields extra clout thanks to prominence of the Iowa caucuses.

The floods across the Midwest have overwhelmed roads and rails and thus trapped millions of barrels of ethanol in the heartland. In a sane world, this wouldn’t harm drivers who just want some regular old gasoline. But thanks to the Renewable Fuel Standard, it’s effectively illegal to sell gasoline without ethanol in it.

Supply curtailed by nature, demand legislated by Congress – blend them together, and you get $4 a gallon in San Francisco and sharply climbing prices in most of the country.

This ethanol squeeze isn’t the only factor pushing up gasoline prices, of course. But pushing up gasoline prices isn’t the only harm of the ethanol mandate.

Ernst and Grassley’s hearing this week will focus on the Army Corps of Engineers and how the federal government can mitigate the harm of future floods. These two lawmakers are perfectly positioned to mitigate the harm future floods will pose to the rest of the country by dropping their stubborn support of the Renewable Fuel Standard.