How to explain the discrepancy—which was, in the case of New Hampshire this week, essentially on the Democratic side of the ballot—between polling numbers and election results? In a column, ABC News’ polling poobah, Gary Langer, makes some suggestions and calls for a “serious, critical look at the final pre-election polls in the Democratic presidential primary in New Hampshire.”
A starting point for this analysis will be to look at every significant Democratic subgroup in the New Hampshire pre-election polls, and see how those polls did in estimating the size of those groups and their vote choices. The polls’ estimates of turnout overall will be relevant as well.
In the end there may be no smoking gun. Those polls may have been accurate, but done in by a superior get-out-the-vote effort, or by very late deciders whose motivations may or may not ever be known. They may have been inaccurate because of bad modeling, compromised sampling, or simply an overabundance of enthusiasm for Obama on the heels of his Iowa victory that led his would-be supporters to overstate their propensity to turn out. (A function, perhaps, of youth.)
Prof. Jon Krosnick of Stanford University has another argument: That the order of names on the New Hampshire ballot - in which, by random draw, Clinton was toward the top, Obama at the bottom - netted her about 3 percentage points more than she’d have gotten otherwise. That’s not enough to explain the gap in some of the polls, which presumably randomized candidate names, but it might hold part of the answer.