Mark Blumenthal | April 8, 2008
Topics: 2008 , Barack Obama , Divergent Polls , Hillary Clinton , Pollster , SurveyUSA
I will admit that, like Pollster reader jsh1120, I am at a bit of a loss about the flurry of recent results from Pennsylvania. In the last week, we have seen surveys released showing everything from an 18-point Clinton lead to a 2-point Obama advantage (for all links, see our Pennsylvania chart and table). Of course, we have had days before this primary season where we saw huge spreads among pollsters in their Democratic primary results.
As before, the most likely explanation involves differences in the kinds of people pollsters are selecting as likely primary voters. In California, Texas and other states with very large minority populations (either African American, Latino or both), the variation in racial composition explained much of the difference. In Pennsylvania, however, the percentage of black voters is relatively low and the Latino population in the low single digits. As such, the mix of gender, age and socio-economic status may help explain the divergent results before us. Unfortunately, only a few pollsters routinely release their composition statistics and most are not asking respondents about their education or income levels. So we are largely left to speculate about the differences.
One way to help clarify the numbers, if only slightly, is to focus on the results among white voters for the recent polls that have tracked and released results by race over the last month. Doing so (see the table below) at least eliminates the differences due to variations in racial composition.
The polls certainly differ, but in many ways, their results are consistent. All four show Clinton with roughly 60% of the white vote in early March. All show modest increase in support (+3 to +7 points) for Barack Obama in recent weeks. They diverge mostly on the Clinton trend. Three of the four show a relatively modest decline in support for Hillary Clinton, while SurveyUSA shows no change at all for Clinton and the smallest increase (+3 points) for Obama.
I am hoping to post more on Pennsylvania -- focusing on the new Quinnipiac University data by race and education -- later today.