Stalemate. Partisanship. The absence of any middle ground. If politicians actually try to govern, these are the challenges that often block effective action. In their book, "Echo Chamber: Rush Limbaugh and the Conservative Media Establishment," recently released in paperback by Oxford University Press, Kathleen Hall Jamieson and Joseph N. Cappella look at one side of the equation: the rabble rousers on the right. They find that an integrated conservative media machine has created a cocoon-like...