Here’s another reason to doubt the blizzard of polls that dominate political talk. Pew, the respected non-partisan research organization, reports that polls
“„[T]here were only small, and not statistically significant, differences between presidential horserace estimates based on the combined interviews and estimates based on the landline surveys only. Yet a virtually identical pattern is seen across all three surveys: In each case, including cell phone interviews resulted in slightly more support for Obama and slightly less for McCain, a consistent difference of two-to-three points in the margin… As implied by these results, in each of the three polls, the cell-only respondents were significantly more supportive of Obama (by 10-to-15 percentage points) than respondents in the landline sample.
“„[A] substantial minority of the cell-only sample is younger than 30 – a demographic group that has consistently backed Obama this year. Traditional landline surveys are typically weighted to compensate for age and other demographic differences, but the process depends on the assumption that the people reached over landlines are similar politically to their cell-only counterparts. **These surveys suggest that this assumption is increasingly questionable, particularly among younger people. **(emphasis added).