Shankar Vedantam has an article discussing research on state of the union addresses. They tend to be more complex in the first 3 years of a presidential term, and less so in the 4th year/re-election cycle. The argument is that the public likes its liquor straight and its politics simple, unmixed with qualifications or cautions. So when a president is running for office he/she keeps things simple, when governing he/she acknowledges more complexity.
It's interesting, though it fits my preconceptions a bit neatly.