Politicians and pundits make a great deal of the imperative for Americans to put aside political differences and "unite" as a nation. Calls for change and fresh approaches to politics beckon citizens to move beyond partisanship and special interests in a new spirit of togetherness. But how realistic is this desire? Isn't the very nature of democracy a process of taking sides? How unified has America been in its past? A casual look at U.S. history...