Today's unusual defeat in the U.S. House of a major farm bill proposal reflects many new dynamics, not the least of which is the urbanization of America.  It proved that House Speaker John Boehner (R-Ohio) was correct last year in calculating that a bill could not be passed in the body, and wrong this year for assuming anything had changed.  The farm bill, which has historically been fought over on regional grounds rather than political partisanship, has now joined most other areas in the battle of left versus right.Domestic food assistance via the SNAP program was ground zero for the philosophical debate over economics.  The right sees food aid growing so fast that it contributes to reduced labor ambition, thus amendments...