So says a new study of the American political system. There are certainly a few Senate and House races that may turn on issues of war, immigration reform, jobs, the economy and federal spending – and the competing candidates’ differences. As two veteran journalists discovered in an exhaustive study of the 2014 primary season for the Brookings Institution, the campaign trail has become largely an information-free zone where political affiliations and party boilerplate count for far more than substantive discourse.