It’s Obama! (Or is it?): Forecasting the 2008 election

Who will win the 2008 presidential election? For those political scientists who specialize in modeling elections with the goal of predicting outcomes, the verdict is already in. Barring some unforeseen or atypical event(s), they have already predicted the winner. Who is it? Before providing the answer, let me first explain the process by which political scientists construct their forecast models.

For years I have told my students that if there is any aspect of political science that can truly be described as a science, it is forecasting presidential elections. Presidency scholars can, with surprising accuracy, predict the winner of the two-party popular vote, within 2-3%, in a presidential election several months before the election takes place. Of course, they aren’t always correct. But they predict the winner far more often than not. In 2004, for example, 7 of the 8 forecast models that I consulted prior to Labor Day predicted George Bush’s reelection that year with an average popular vote of about 53%. He actually won with about 51%.

How do they do it? How can political scientists predict elections before any of the events that the media emphasizes – campaign advertising, debates, and the other myriad daily incidents on the campaign trail – have occurred? They begin with a basic premise: that the voting public, in the aggregate, is rational. That is, voters can differentiate the two candidates, broadly speaking, along an ideological continuum, and generally vote for the candidate who falls closest to their own political views. Moreover, voters are aware of how things are going in the world, based on tangible measures – gas prices, food costs – and by paying at least limited attention to the news and through conversations with family, friends, and coworkers. As political scientists, then, if we can create measures for “reality”, and for voters’ preexisting political preferences, we can construct a reliable forecast model. That’s the basic approach adopted by all these forecasters, although their models differ in the particulars.

There are a variety of forecast models, then, but they all are based on some variation of the following approach. First, establish some measure for the state of the economy, such as the unemployment rate, or the quarterly change in the Gross National Product, since most voters pay attention to the economic health of the nation and often vote the nation’s “pocketbook”. Second, measure the partisan distribution of voters in country – how many people call themselves Democrats? Republicans? This is crucial to forecasting, because party affiliation is the single bigger predictor of the vote in a presidential election. Most voters tend to view politics through a partisan prism that colors their evaluation of candidates and issues, and they typically support the candidate who shares their party preference. Democrats may not know the details of Obama’s health plan, but they know he’s a Democrat, and that tells them they are likely to favor his plan over McCain’s. So if forecasters know the partisan breakdown of the likely voters, it helps establish a baseline for predicting the presidential vote.

All forecast models are predicated on an expected level of turnout among voters. Some also include additional variables that measure how long one party has occupied the presidency, or the popular approval of the current president, in order to assess the pressure for “change” in Washington.

In sum, the typical forecast model predicts the distribution of the two-party vote as a function of economic conditions, the partisan breakdown of voters, approval ratings of the party or president in the White House, projected turnout, and sometimes, length of time the incumbent party has held office.

Note what these models seem to ignore: campaign advertising, debates, the daily tactical skirmishing between candidates that forms the gist of campaign reporting – indeed, almost the entire general election campaign! And yet they have accurately, within a specified margin of error, predicted the victor in almost every presidential election dating back to 1980. (I will deal with the “almost” in a separate post). Forecasters ignore the daily minutia of campaigns because, for the most part, they believe that fundamentals drive the vote, not campaign tactics. Both candidates will try to “frame” the campaign in a way that is most advantageous to them. For Obama, that means characterizing this election as a choice between change and four more years of the “failed” Bush-Cheney policies. For McCain, it is also about change, but change driven by a maverick who has the experience to do what is necessary to guide the nation in perilous times. For forecasters, these efforts largely negate one another; few voters are persuaded by the campaign advertising and debates to abandon their long-standing predisposition to vote for the candidate of their preferred party. Indeed, polls show that already 80% of the electorate has made up their mind regarding which candidate they will support this year.

In short, the models work because voters are rational. They don’t make a blind leap of faith in the voting booth. Instead, they base their vote on a retrospective evaluation of how things are going under the current party in power and a prospective estimate of how things are likely to go if they change parties or not. Each candidate, meanwhile, will do his best to frame the campaign using the raw material the political environment provides, but they can’t simply create a reality that is at odds with what the voters see. As a result, campaigns may be more or less effective in mobilizing voters to come out on Election Day, but they tend to have very little persuasive effect regarding how voters cast their ballot.

But what about the undecided voters – those 15-20% of the electorate, most of whom are independents, that don’t decide for whom to vote until the last two weeks? Forecasters assume that their vote will break down roughly according to the distribution of the more partisan voters, so that these late voters typically do not change the outcome of the race.

This is a very simplified and abbreviated explanation for how presidency scholars construct their forecast models. You will undoubtedly question many of these assumptions – as you should. Rather than try to anticipate all your objections, let me instead tell you what the forecasters are predicting for 2008. Then I will try to respond to the inevitable barrage of criticisms. Please post your comments on my website if possible, since I anticipate a rather vibrant discussion on this topic. And now, without further ado, here are the forecasts for this election. I list the date of the forecast (notice most are made prior to the party conventions), the name of the forecaster, and the percentage of the two-party vote that they predict the Republican candidate will receive. Drum roll, please:

09/08/2008 Jim Campbell 52.7

09/03/2008 Andreas Graefe and Scott Armstrong    48.0

08/28/2008 Michael Lewis-Beck and Charles Tien 49.9

09/05/2008 Tom Holbrook 44.3

06/30/2008 Brad Lockerbie    41.8

08/27/2008 Alan Ambrowitz 45.7

08/02/2008 Charles Bundrick and Alfred Cuzan   48.0

08/28/2008 Robert S. Erickson anbd Christopher Wezlien 47.0

07/28/2008 Carl Klarner    47.0

06/07/2008 Doug Hibbs, Jr.   48.2

07/31/2008 Ray Fair    48.5

01/15/2008 Helmut Norpoth 49.9

09/08/2008 Average Forecast of Republican Share of the Popular Vote: 47.6

Note that these models differ in their particulars. I can discuss the details of the models if you’d like. Not all are equally reliable, based on past performance. Nonetheless, they all – with one exception (the Campbell forecast), project that Barack Obama will win the 2008 popular vote. The average predicted share for McCain is just under 48%, so the election will be close. But given the margin of error of most of these forecast models, we can safely assume that Barack Obama will be our 44th president. 

Or can we? Before assessing potentials pitfalls in these forecasts, I’m eager to hear your reactions. Do you trust these projections? Why or why not?



  1. But Matt, where is YOUR prediction ?

    Given that the predictions are a measure of the popular vote, I would imagine that unless the vote is close, the electoral vote would represent the popular vote, hence the margin of error in the predictions is very critical. Can you comment on this ?

    It would be interesting to know to what quantitative extent the above sources have been succesful in prediction the vote outcomes of past elections. Ascribing a confidence level based on this (a weightage if you will) would perhaps be useful rather than carrying out a simple arithmetic average..

    As you had stressed in the past, this is an election of many firsts. One for which there is, as I understand it, quantitative data is the discrepancy between intent and action in voting for black candidates. Are there other such effects that can be factored in along with this ?

  2. Before I decide whether to trust these projections, I’d like to see how these models did in another extremely close election: Bush-Gore 2000. Was Bush the safe bet then, according to these forecasts? (Or was that very election your “almost”?)

    Next question: what effect does the historical success of these models have on the controversy surrounding rational choice theory as a methodology for political scientists? Do forecasts like these work as well on smaller scales like, say, local or state elections?

    Lastly, and somewhat facetiously: if these models have been working accurately for many elections, predicting the winner with the accuracy Professor Dickinson cites, how come Presidential elections in this country are dragged out for so damned long? Doesn’t this make the daily campaign tit-for-tat moot? If the winner is predicted so far in advance, why bother with tracking polls, debates, gaffes, and sleazy campaign ads?

    Having asked all this, I wonder how these methods differ from things like the Iowa Electronic Markets…

  3. I am so glad they guessed at the national popular vote, considering that does not mean a single thing in an election. They should be guessing (forecasting) and the Electoral College vote and if they need to, explain the three or four critical states in this election: Colorado, Virginia, Ohio and possibly Pennsylvania or Florida. That makes a heck of a lot more sense than just giving % of vote received.

  4. I’m late to the party, but…

    So great. Elections equals economy plus voter identification.

    Therefore, if you want to win the next election, you should get more people to identify with your party.

    Until political scientists can identify and model the factors that underlie voter identification, I’m not sure they’ve produced anything of real use.

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