President Barack Obama and Mitt Romney are in a battle for the trust of the middle class. The group might be hard to define, but most Americans say they are part of it, and many swing voters fall into it. Accordingly, both camps roll out the term frequently in their campaign ads. The Obama campaign has a new ad called "Pay the bills." It features a woman named Christie who describes a very ordinary life: Christie: "I do the laundry. I pay the bills. I make sure ...