The U.S.C./LAT poll is no exception, but it makes two unusual decisions that combine to produce an odd result. You can read more about the U.S.C./LAT “past vote” issue in this August article, but the big problem is that people don’t report their past vote very accurately. If the survey didn’t include a past vote weight, the past vote of its respondents would be Obama 38, Romney 30. This is a lot like national surveys that were published around the same time as the U.S.C./LAT poll, like those from NBC/WSJ or the NYT/CBS News. The U.S.C./LAT poll weights for all of these demographic categories; it just weights to smaller groups.

Source: New York Times October 12, 2016 16:51 UTC