Why Gallup Understates Obama’s Support

Mark Blumenthal: “The misses were typically small — usually within a single percentage point, although sometimes slightly bigger — but they made a consistent impact on the non-white composition of Gallup’s samples. Instead of achieving the target of 12.1 percent black set by the March 2011 CPS, the average across the seven surveys was 11.3 percent black. Instead of hitting the CPS target of 13.7 percent Hispanic, the seven surveys averaged just 12.4 percent Hispanic.”

But he notes the “real story here is less about Gallup than about the new reality
of public opinion polling. Sophisticated random samples, live interviews
and rigorous calling procedures alone can no longer guarantee accurate
results. Today’s rapidly declining response rates require more weighting
than ever before to correct demographic skews, a phenomenon that places
growing stress on previously reliable weighting procedures.”