On most issues, the extreme positions increasingly define the respective parties' current policy positions. This leaves little room for reasonable compromise. It also means that our political debates tend to devolve into ad hominem attacks that merely provoke defensive reactions. Until we share a common enemy, we are doomed to perpetually squabble with one another and avoid any chance for harmony. Fortunately, the country tends to run itself fairly decently without resolution of our most cantankerous disputes.