(The editor of AmericanHeritage.com asked for our thoughts on why Presidents’ second terms so often go badly, and whether it has anything to do with the 22nd Amendment, which limits them to two terms.)
Several factors are involved. The first is simple regression toward the mean. To get reelected, you have to have good luck in your first term. During the second term, chances are your luck will be merely average, so it will look like you did a worse job. (This also explains why the Red Sox didn’t win the World Series this year.) A related factor, similar in concept but less random, is the business cycle. If the economy goes well in your first term, it will probably get worse sometime during the second, and people will blame it on you.