In Frank Darabont's modern classic, The Green Mile, Tom Hanks' Paul Edgecomb character had a hard and fast code of conduct for the Mile.
Men under strain can snap. Hurt themselves. Hurt others. That's why our job is talking, not yelling. You'll do better to think of this place like an intensive care ward in a hospital.
Similarly, voters are flocking to Senator Obama partly because he's a Paul Edgecomb style leader. Strong, calm and even-keeled in the midst of our present economic uncertainty and crisis. Americans of every walk of life are worried. Retirement funds have lost $2 trillion dollars. People are losing their houses and their healthcare. We're all under tremendous strain.
So the last thing we want is an erratic, spasmodic crank and an airheaded, out-of-her-depth, screeching coward. This Republican ticket is Percy, and Americans are rejecting it.
ADDING... Elvis has a good point in the comments about Wild Bill. Let's say McCain is Percy and Palin is Wild Bill.