All this election season, I have pointed out that a transparent statistical snapshot of
state polls gives the clearest look at the ups and downs of the Presidential race. Nonetheless pundits, especially on the right, asserted that pollsters as a whole were biased – even attempting to “unskew” the bias. However,
the bias in state polls turned out to be close to zero – certainly less than 1.0%, based on Florida. To pollsters in 2012, the state-level problem is a correctly solved problem.
However, the same cannot be said of
national polls. In final surveys, the national average* Presidential margin was Obama +0.31 +/- 0.37% (mean +/- SEM). The actual margin is currently Obama +2.74%. Therefore
on average, national polls were biased by 2.4 +/- 0.4% toward Mitt Romney.
With this number in hand, it is now possible to perform the ultimate unskewing – bringing polls into alignment with reality by adjusting them toward Obama. Here, then, is the “first draft of electoral history” at the national level.
From this graph, three facts are evident:
President Obama led national opinion on every single day of the final two months of the campaign.
During this period, the only event to meaningfully move national opinion was Debate #1, which led Mitt Romney to close two-thirds of a 6-point gap between him and President Obama – overnight. Some of this gain was reversed in the closing two weeks of the campaign.
Sandy’s measurable effect on opinion was no more than 1.0%, and even this might have reversed by Election Day.
So Bickers and Berry’s claim that “the president clearly benefited from the ‘October surprise’ of Superstorm Sandy” is unsupported by data. I am developing doubts about their analytical neutrality. A second piece of evidence is that most econometric models pointed in the opposite direction to theirs. A prominent example is the prior that informed Drew Linzer’s analysis at Votamatic.com.
http://election.princeton.edu/2012/11/12/the-final-unskewing/
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