The Democratic presidential candidate is the avant garde of the new artpolitical era. By Crispin Sartwell, CRISPIN SARTWELL teaches art and art history at Dickinson College. His latest book is "Six Names of Beauty." From the Los Angeles Times, July 5, 2007, Copyright 2006 Los Angeles Times IN MANY ARTS, such as painting, poetry, woodworking and arrogance, Americans have made significant contributions. We have few rivals when it comes to growing marijuana or blowing stuff up. But in one art we are as inventive as small appliances or perhaps cucumbers.