Mother Nature is our best teacher and the only one who is always right.
- Viktor Hamburger, biologist
In yesterday’s Los Angeles Times, several prognosticators (including me) commented on why we were right or wrong. On the wrong side are Colorado researchers Bickers and Berry, who thought that Romney would get 330 electoral votes. Now, they offer a convoluted explanation culminating in something about Hurricane Sandy. Their wrong answer reveals a persistent false idea that is circulating in some circles.
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.
I do want to correct one error in the LATimes piece – the cartoon. It is not true that “Democratic” math somehow beat “Republican” math. Instead, what we saw in this race was a triumph for the expertise of a profession of experts whose job it is to measure public opinion: pollsters. As a community, they did very well at surveying state opinion – as they have since 2000 in my memory, and perhaps earlier.
There is one remaining finding that puzzles me. Although post-debate-#1 national poll averages did not move much in October, state polls did – toward President Obama. There is some unexplained discrepancy. Were swing-state voters more malleable by messaging and advertisements? Were they more attentive to the race? Did these swings occur at the national level too, but polls failed to pick it up? Hmmm.
*This time I’m using the average. The median Election Eve poll margin was Obama +0.0 +/- 0.95% – even worse performance.