Over the weekend Republican-leaning commentators at Nate Silver’s 538 Blog have been advancing the theory that President Obama’s victory can be attributed to “Superstorm” Sandy which hit the Northeast on October 29th, just a week before Election Day. What especially irked Republicans was the reaction of New Jersey Governor Chris Christie who embraced the President in the wake of the storm despite having delivered the keynote speech at the Republican National Convention and being an active spokesman for Governor Romney.
The view that Christie “threw Romney under the bus” and thus assured the President’s re-election was the polar opposite of Republican commentary right after the storm hit. Spokesmen like Rudy Giuliani criticized the President for campaigning in Western states like Nevada when New Jersey and New York had been ravaged. Liberal commentators like John Cassidy at The New Yorker naturally took the opposite view, suggesting that the President’s “handling of Sandy has raised his standing, and his poll ratings.”
I find neither of these arguments convincing. First, many of the claims about a late Sandy-based surge in the polls rely on differences in the President’s level of support that fall well within the margin of error. Cassidy, for instance, points to a three-point swing in Pew’s results as evidence, a change that could just as easily be attributed to sampling variability. Including a term in my model for polls conducted after Sandy showed a pro-Obama effect of one percent, but it, too, did not achieve statistical significance.
Rather than looking at the pre-election polls, I suggest we examine the exit polls taken on Election Day. Looking at the national exit polls, we might conclude that Sandy had a large effect. Fully 15% of voters reported that Sandy was “the most important factor” in determining how they voted, and 73% of those people reported voting for Obama. To anyone accustomed to analyzing surveys, this 15% figure seems implausibly high. For 15% of the national electorate to attribute their vote to Sandy, when the vast majority of them lived outside the affected area, is hard to comprehend. Moreover, despite the obvious correlation between attitudes about the storm and support for the President, the direction of causality is questionable. An equally plausible explanation for this correlation is that both answers reflect the partisanship of the person being interviewed.
We might thus wonder what effect the storm might have had on voters in swing states like Ohio, or even Florida with its history of hurricanes. Unfortunately, if we drill down to the individual state exit polls, we find that this question was asked only among voters in New York and New Jersey, states whose outcomes were never in doubt. Even voters in neighboring states like Pennsylvania and Connecticut were not asked about Sandy. (No exit polling was conducted in Louisiana this year so we cannot assess the claim that voters in that state might have been more attuned to the issue because of their experience with Katrina. Mississippi voters were polled but not asked the Sandy question.)
In order for the hurricane to have affected the outcome of the election, we would need to see its effects in the swing states where the election was actually decided. Since we do not have direct measures of peoples’ opinions about the effects of the storm in these states, and because such answers are inherently untrustworthy, we have to look at a more indirect measure of Sandy’s effects. We can compare the opinions of voters in the swing states who reported deciding between the candidates in the last days before the election and see whether we can detect a late movement toward the President in the aftermath of the hurricane. Here are the results from the exit polls in the nine swing states I examined before.
The chart shows quite clearly that, if anything, late deciders broke more in favor of Governor Romney than President Obama. Of voters who made up their minds in October or earlier, the President’s average lead in these nine swing states was about five points. Among voters who decided during “the last few days” before the election or on Election Day itself, his margin shrank to just over a percentage point.
More importantly, we can determine how large a contribution each group of voters made to the overall margin between the candidates. Take Wisconsin as an example. Late deciders made up 10% of the electorate in that state, and those voters favored Romney by eight points. Taken together we can attribute an effect on the overall margin of 10% times 8%, or 0.8% in favor of Mr. Romney. The other 90% of Wisconsin’s voters favored the President by 10%, for an overall effect on the margin of 9.0% in favor of the President.
The average effect of the decisions of late deciders in these nine states is zero compared to a four percent margin in the President’s direction among voters who decided in October or before. Thus there is absolutely no measurable effect of Superstorm Sandy on the results in these swing states. If anything voters who decided after the storm hit showed a slight preference for Mr. Romney in comparison to voters who decided before.
