Thomas Friedman wrote a good column on the dangerous level of divisiveness in this country - "Where Did 'We' Go?", New York Times, 2009-09-29.
He compares the situation in Israel before Yitzhak Rabin was assassinated in 1995 with the situation in the United States now. He thinks the vitriol in much of the anti-Obama rhetoric is going to lead somebody to take extreme action.
He also thinks that the level of criticism leveled at all presidents since 1992 has made it difficult for them to govern. He postulates that George H. W. Bush was the last "legitimate" president.
I was going to add a comment about the need for a viable third party when there were 42 comments, but I had to be elsewhere. When I got back there were 201 comments and a note that "Comments are no longer being accepted." Now, nearly 8:30 in the evening, there are 393 comments!
I did read or skim the 201 comments. They ran from the very thoughtful to the very shallow and divisive. The worst were those that divided left and right with one being good and the other being bad, depending on the persuasion of the writer. I had less sympathy for many on the right because they didn't consider the degree of difference in criticism of presidents. There is a big difference between satirizing a president and creating lies about a president. There is a big difference between calling a president an idiot (aren't they all in one way or another?) and saying that president was not born where he was.
Interestingly, the critics on the right say that the "liberal media" don't criticize the president. Let's see, Steve Sack of the Star Tribune and Garry Trudeau of Doonesbury have drawn cartoons criticizing Obama.