Boredom

Boredom, the sociologist Robert Nisbet wrote, is among the universal and insistent forces driving human behavior. Mankind's nervous system evolved during millions of dangerous years (saber-toothed tigers, etc.). Now, however, mankind has suddenly, in a few millennia, encountered the monotony of orderly life, which bothers human brains formed by and for hazardous circumstances.
Among the cures of boredom that Nisbet listed are war, murder, revolution, suicide, alcohol, narcotics and pornography. He might have added presidential politics.

George F. Will, Sunday, March 4, 2007; washingtonpost.com