I am impressed with the response to my question yesterday. Readers, go see the comment thread. Also, thank you all for the kind words. Yesterd...
General overview 2012: the state of play
Welcome to all the new readers. Traffic is booming.
First, a brief update. Several weeks ago I showed that convention bounces (and other fluctuations) are uncorrelated with the final outcome. However, it is fun to look at them. In the next 1-2 days, I will give a final measure of the GOP’s post-convention bounce, which is zero or negative. I note that a “negative bounce” is highly unusual.
Since many of you are new, I will take time today to give a general overview of the state of play. The Princeton Election Consortium’s analysis and prediction approach gives a sharp picture of where we are at: very likely Obama re-election, with House and Senate on a knife edge.
The Presidential race is largely determined. The national media is correct that this year’s Presidential race is close. And voters are polarized: as few as 1-2% of voters are persuadable.
However, the media have failed to clearly spell out the logical consequence that the Presidential race is also very stable. President Obama has kept an electoral lead every single day since May. Based on the statistical behavior of polls in past re-election races, his November re-elect probability is 88%. Conversely, the probability of unusual movement or a black-swan event is 12%.
Both Senate and House control are on a knife edge. We have an unusual situation this year: control of both houses of Congress is up in the air. This recalls the elections of 1994 (GOP takeover during Clinton’s first term) and 2006 (Democratic takeover in GW Bush’s 2nd term). What’s different is that 2012 is a Presidential election year, so voter attention is higher. This will have profound consequences for Obama’s probable second term (and for Romney’s less probable first term).
Campaign funding will affect Congress more than the Presidency. This year the Citizens United ruling will have a major impact. Because money is most effective in marginal cases, spending will be most effective in Senate/House races – not at the Presidential level. This is true whether you are a Democrat or a Republican. It is why Karl Rove’s Crossroads GPS is not focused on the Presidential race. And it is why I have set up the ActBlue page at left. Republicans can use the NRSC.
Now, a few words about the methods by which I reached these conclusions.
The state poll Meta-analysis. The first step in our Presidential analysis is to use state polls to provide a snapshot of conditions today. As in past years, I use outlier-resistant medians to generate a probabilistic calculation using Electoral College mechanisms. The result is two outputs: an electoral vote median with a 95% confidence band, and a Meta-margin. They are updated every day at 8AM, noon, 5PM, and 8PM.
On Election Eve, the EV estimator lands on the final election outcome within approximately +/-5 EV. So the snapshot (in the top line of this site) tells us where the race is at any given moment with very high accuracy.
The Meta-margin is very special. It tells us how far the race would have to shift to create a electoral near-tie. It is like the standard national-poll margin you see in the news, with two differences: (1) It is in the units that matter, the Electoral College, and therefore closely reflects swing state movement. (2) It is more accurate than any poll aggregation you will find elsewhere. Its typical precision is +/- 0.2%. By this measure, today Obama leads Romney by 2.0%.
New for 2012: a prediction. This year I draw upon the statistics of past-year races to make a prediction for the November election. This calculation does not use other variables (unemployment, campaign spending, bounces) because they fail basic tests for good model-building.
From now until September 27th, I am giving a long-range outlook, analogous to long-range weather prediction. After that, I will replace the long-range outlook with a shorter-term prediction. In the meantime, what we have is this:
As of the end of August, the long-range electoral prediction is 283-353 EV (1 sigma, the red zone) and 250-360 EV (2 sigma, the yellow zone). The two-candidate vote share prediction is Obama 51.6 +/- 1.1% (1 sigma).
Noise that is not included in this analysis. I do not use any econometric variables, on the grounds that these simply add noise. One consequences, as I showed yesterday, is that the Meta-analysis has extremely sharp time resolution to detect bounces and shifts.
Commenters. If you are curious about any of these topics, the comment threads on this site are curated and are of relatively high quality. They are worth browsing.
There is much more to write about. But I’ll stop there.