A bit more below cut.
Both parties have a "base" that views its opponents as downright evil. It is not enough for one side to be mistaken or naive or idealistic to a point of ignoring real hardship. No, the other side are downright evil. They want to turn our beloved Republic into a tyrany in which the other side exercises absolute control for the benefit of our hated enemies, foreign and domestic.
This holds equally true for those who believe Republicans are religious fanatics, racists and greed heads sprinkled with morons, or believe that the Democrats are militant athiests out to take away our guns, suppress our rights, steal our property and wealth and give it to people who don't deserve it. And, of course, there is more than enough evidence for either side - including the lengthy list of grievances suffered -- to justify this view.
Which leads us to Obama and McCain being repeatedly told to "take the gloves off" by partisans who believe the other side are so morally disgusting that if only the campaigns and the media would "tell the truth" about the other side, the entire rational world would totally agree that the other candidate is unfit to share a dinner table with decent people, let alone run the country. Becuase it is just so obvious that the only reason someone wouldn't believe this basic truth is because they are either (a) ignorant of the true nature of the other candidate, or (b) themselves an evil person.
Which is why we have John McCain trying to calm his own supporters that if Obama wins, it is not the end of the world and a cause for armed revolt. Similarly, Obama is trying to make it clear that he is going to work with Republicans and not shut them out of government. And this does not play well with the "base."
One of the transformative elements of this election is the likelihood that many people will vote -- far beyond the totals of either base. My hope is that this will move us away from the need to portary the other side as enemies of freedom.
Mind you, we also need to discover that you can (and should) say "you're wrong" and even "you're policies are an utter catastrophe" without saying "and you are evil for even thinking such things." I was going to say "redscover," but the fact is that this rationality is rarely the case.