Assessing the forecast models: Some caveats

Yesterday I provided the results from several forecast models, all of which – with one exception – predict that Obama will win the two-party popular vote over McCain. Historically, of course, the popular vote winner is usually the Electoral College winner. (In a later post I’ll examine the likelihood that this won’t be the case this year.)  On average, the models have McCain winning only about 48% of the popular vote.  These forecasts, I suggested, have a strong track record.  But they are not infallible.  Although they all (with one exception) correctly picked Bush as the popular vote winner in 2004, most of them were wrong in 2000. “It’s not even going to be close,” Michael Lewis-Beck said then, predicting that Al Gore would win 56.2% of the 2000 two-party popular vote. James Campbell had Gore winning with 52.8% .The most conservative model, by Alan Abramowitz, had Gore winning 53% of the vote. Thomas Holbrook gave Gore 59.6% of the vote. Christopher Wleizen had Gore receiving 56.1% of the 2-party vote. (These names should be familiar to you since I’ve included their 2008 forecasts in my last post).  As you know, Gore did win the popular vote, but came nowhere close to the percentages most models predicted; he actually received 48.4% of the popular vote with Bush coming in a close second with 47.9%.  (In case you are wondering, I also predicted Gore to win the 2000 race, but with 49.5% of the popular vote. Of course, I never envisioned that he would lose the Electoral College).  In retrospect, the forecasters who missed the 2000 election had a number of explanations for why their models were wrong, but a big chunk of the blame, they argued, is that Gore simply failed to capitalize on the positive fundamentals – a budget surplus and relatively strong economy (although an economic slowdown was just beginning) – that should have kept the incumbent party in power.  Instead, he ran a populist-based campaign that emphasized change while trying to separate himself from Clinton’s legacy. Now is not time to debate the Gore campaign strategy from eight years back.  The more important point is that these forecast models sometimes miss the mark.  This is a reminder that these models are predicated on some basic assumptions that are worth reviewing:

First, they presume a two-candidate race.  In 1992, Ross Perot jumped into the race as a third-party candidate, winning almost 19% of the popular vote and perhaps costing the incumbent George H. W. Bush reelection. Bill Clinton was elected instead, with 43% of the vote, while Bush won only 37.4%.   However, I don’t see a strong third-party candidate running in 2008, although in a close election it is possible that a Bob Barr (the Libertarian candidate) or perennial candidate Ralph Nader might influence the outcome of a particular state, as Nader did in Florida in 2000.

Second, the models don’t predict the Electoral College vote.  In later posts I will begin examining the likely outcomes in key battleground states that will determine who wins the Electoral College. Forecast models are predicated on the assumption that whoever wins the popular vote will win the Electoral College vote as well. This is usually a safe assumption – but not always!

Third, and perhaps most importantly, the models assume that each candidate runs an equally effective campaign.  That is, the two candidates understand how best to frame reality in ways that redound to their comparative advantage, and do so effectively.  We don’t expect McCain to run on his youth, or Obama to tout his war record – that would be at odds with what the public knows about these candidates. Instead, they try to emphasize their strengths and tout their opponent’s weaknesses .

Finally, the models expect that voters will behave in this election much as they have in past elections: using a combination of retrospective evaluation of the party in power and prospective assessments of what is likely to happen if a new party is put in the Oval Office, and they vote according to which scenario is best for the nation, broadly speaking.

Now, is there anything unique about this election that might cast doubt on some of these assumptions?   At first glance, I can think of several aspects of this election that might throw these models off.  They are, in no particular order: race, gender, the lack of an incumbent in the race; two senators heading the major parties’ tickets, the impact of the internet/blogosphere on election coverage and the proliferation of polls.  Any one of these factors could, potentially, disrupt the “normal” vote in a way that might cast doubt on the assumptions built into these forecast models.  But will they?  In many respects this has been an unprecedented election.  In other ways, however, it actually has reinforced political scientists’ basic understanding of the forces that drive most presidential elections. In my next several posts I will examine some of these issues to see if we can estimate what impact, if any, they will have on the general election. Because of the debate scheduled for Friday, I want to begin by discussing the role past debates play in influencing election outcomes.

But what do you think?  Which of these factors, if any, might affect how voters cast their ballot in 2008?  Are there other factors that might come into play in this election?

One comment

  1. I’m curious about the factor of actual policy issues. Although party association is a clear indicator…could the candidates position and reactions to the current economic turmoil between now and the election have any impact considering the significance of that issue?

    Secondly, the media loves to play up “who won” in these debates, and I know you’re going to talk more about debates this week, so this question will probably be answered then, but do they tend to sway voters at all? A follow up to this question is specifically in regards to the vice-presidential debate. Will the Sarah Palin factor lead that debate to be more influential than previous VP debates?

    Finally, you mentioned proliferation of polls as something that may throw the models off…what do you mean exactly? I wasn’t entirely clear on that observation. I’m looking forward to the debate commentary.

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