Co-blogger Orin Kerr is right to point out that many partisans are engaging in overheated rhetoric and unfair charges against their opponents. This problem is not unique to recent American politics. If you look at our very first contested presidential elections (Jefferson vs. Adams, 1796 and 1800), you will find ridiculous "deranged" charges every bit as ludicrous as those we hear today (e.g. - claims that Jefferson was a close atheist who would destroy all religion; accusations that he would betray the country to France; claims that Adams and the Federalist Party were secretly plotting to establish a monarchy, and so on).

I. The Role of Rational Political Ignorance.

Why this longstanding pattern of overheated and ridiculous political rhetoric? Regular readers of this blog won't be surprised to learn that I think it has a lot to do with widespread political ignorance. Overwhelming evidence shows that much of the public knows very little about politics and public policy. For individual voters, such ignorance is perfectly rational because there is very little chance that your vote will actually influence the outcome of an election. But the less you know, the more you are susceptible to inaccurate and extreme charges. People who are familiar with the details of Barack Obama's biography are unlikely to believe that he is a secret Muslim who sympathizes with terrorists; not so those who know little or nothing about him. The same goes for similarly ridiculous charges against the Republicans. As a result, candidates and activists have incentives to make ridiculous charges because they know that many ignorant voters will believe them.

II. The Role of Biased Evaluation of Political Information.

Even some of those voters who do know more than the average citizen are still susceptible to overheated charges. Rational ignorance implies not only that people have little incentive to acquire political information, it also means that they have little incentive to make rational judgments about the information they do acquire. As a result, most of use evaluate political information in a highly biased way, overvaluing anything that confirms our preconceived views and resisting new information that seems to undercut them. This helps explain why many otherwise intelligent people come to endorse ridiculous political conspiracy theories. For similar reasons, it helps explain why otherwise intelligent political partisans embrace "deranged" accusations against their political adversaries.

Can any of this be changed? Maybe. But two centuries of political history suggests that it will be extremely difficult to do so. "Derangement syndrome" may be an inevitable aspect of democratic politics, especially when elections are closely contested and involve divisive issues.