Wednesday, September 17, 2008

Diverging Virginia Polls

In response to several inquiries, I just sent this e-mail to our Virginia press list:

I have received several questions about the disparity between our Public Policy Polling survey today showing Barack Obama with a two point lead in Virginia and a Christopher Newport University survey showing John McCain leading by nine points in the state.

While only the election will answer who is right or wrong, the demographic composition of the polls can easily be compared to the state’s demographics.

About 20% of Virginians are black and according to the 2004 exit polls for the state, 21% of voters that year were black. PPP projects blacks to make up 22% of the electorate, while Christopher Newport projects blacks to be less than 10% of the electorate.

To put this into voter turnout figures, for the Christopher Newport survey to be correct there would have to be 55% turnout from non-black eligible voters, while only 25% of black eligible voters would have to turn out. PPP thinks that black voters and those who are not will turn out at roughly equal levels.

There is also an age disparity. We project that 44% of the electorate will be under 45 years of age, while Christopher Newport anticipates only 12% of the electorate being under the age of 40. According to the 2004 exit poll 49% of voters were under 45.

A poll that significantly undercounts young and black voters will also significantly undercount support for Barack Obama. It is vitally important to look at the demographic compositions of polls and how they compare both to the demographics of the state and those of past electorates when trying to sift through disagreements like the ones found in today’s polls.

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