Last Thursday, the New York chapter of the American Association for Public Opinion Research (AAPOR) held a post-mortem on "What Happened" to the polls in New Hampshire. The meeting included a presentations by pollsters from Gallup, the Marist Institute and CBS News on the polls conducted by their own organizations. Gary Langer, the ABC News polling director, blogged a complete report on the discussion that is well worth reading in full. Some highlights follow.
Gallup's Frank Newport attributed "half of the misstatement" of their poll to their likely voter model:
Gallup, whose final poll had Obama ahead by 13 points, had a closer 5-point Obama lead among people who described themselves as registered voters. That means its likely voter modeling, used to produce a more accurate estimate of who’ll actually vote, instead introduced error.
Gallup’s editor-in-chief, Frank Newport, said the modeling included factors such as enthusiasm and attention to the race, both of which may have increased for Obama and slacked off for Hillary Clinton after Obama’s Jan. 3 victory in Iowa. Unlikely voters – those excluded from the model – were much better for Clinton. “Obviously that was a cause for the incorrect likely voter numbers that Gallup put out,” he said.
The conference also featured the first discussion of post-election follow-up surveys conducted by both Gallup and the Marist Institute:
Newport and Miringoff based their conclusions partly on post-election polls in which they called back respondents to their pre-election polls in an effort to see where those polls went wrong. Analysis of those data is not complete, though Newport said Gallup hopes to post some conclusions on its website next week.
Both said their callback polls reached about two-thirds of the original poll respondents; they hadn’t yet weighted these samples to adjust for the noncoverage, a step that could improve their analysis.
See the full article for some additional details on the call back surveys and a discussion of their potential pitfalls.