The failure of the New Hampshire pre-election surveys to mirror the outcome of the Democratic race is one of the most significant miscues in modern polling history. All the published polls, including those that surveyed through Monday, had Sen. Barack Obama comfortably ahead with an average margin of more than 8 percent. These same polls showed no signs that Sen. Hillary Clinton might close that gap, let alone win.
While it will take time for those who conducted the New Hampshire tracking polls to undertake rigorous analyses of their surveys, a number of things are immediately apparent. First, the problem was not a general failure of polling methodology. Second, the inaccuracies don’t seem related to the subtleties of polling methods. Third, the mistakes were not the result of a last-minute trend going Mrs. Clinton’s way. Fourth, some have argued that the unusually high turnout may have caused a problem for the pollsters. It’s possible, but unlikely. To my mind all these factors deserve further study. But another possible explanation cannot be ignored — the longstanding pattern of pre-election polls overstating support for black candidates among white voters, particularly white voters who are poor.