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Presidential Election Forecasting

 

DeSart and Holbrook Forecast Model

Dr. Jay DeSart, Associate Professor of Political Science - Utah Valley University
Dr. Thomas Holbrook, Wilder Crane Professor of Government - University of Wisconsin-Milwaukee

UPDATE - The final Election Day update of our rolling forecast model now predicts that Barack Obama will win the election with 51.37% of the national 2-party popular vote to Mitt Romney's 48.63%.  The model also predicts that Obama will win the presidency with 303 electoral votes to Romney's 235.  Based on these results, there is a 88.62% probability that Barack Obama will win the election.   Details



UPDATE: Election Night: The Paths to 270 - What our model suggests you should look for, and when to look for it on election night.



October 3, 2012 - The election forecast model we have developed predicts a victory for Barack Obama over Mitt Romney on November 6th.

The model, which is based on state and national polling data as well as state historical voting patterns, predicts that President Obama will receive 53.13% of the national 2-party popular vote to Mitt Romney's 46.87%. Furthermore, the model predicts that President Obama will win the Electoral College vote, 332 - 206.

The model that we have used to generate this forecast was originally published in the International Journal of Forecasting in 1999, and has undergone significant refinement since that time. Our most recent update was presented at the 2009 Meeting of the Western Political Science Association, and was ultimately published in Putcha, C., ed. Methods of Forecasting American Election Outcomes. Lewiston: Edwin Mellen Press, 2010.

It has been used to generate fairly accurate predictions of the last two presidential elections.  Our research, which looks at data from the elections from 1992 - 2008, shows that the model correctly predicts just over 90% of all state outcomes, predicts the national popular vote to within an average of 0.5% of the 2-party vote, and predicts the Electoral College vote to within 24 Electoral Votes.




Here are the state predictions, along with their respective win probabilities, as projected by the model:
ObamaRomney
StateWin
Probability
StateWin
Probability
Virginia63.6North Carolina70.8
Colorado66.2Missouri74.5
Florida71.2Arizona85.0
Ohio81.0Tennessee90.6
Nevada83.2Indiana93.9
Iowa87.6West Virginia94.7
New Hampshire90.9South Dakota95.9
Wisconsin93.5Montana96.0
New Mexico95.7Louisiana97.9
Pennsylvania96.2South Carolina98.6
Oregon97.4Georgia98.9
Minnesota97.6Mississippi99.1
Michigan98.5Arkansas99.1
New Jersey99.9Kentucky99.2
Washington99.9Texas99.5
Maine100North Dakota99.7
Illinois100Kansas99.9
Connecticut100Alabama100
California100Nebraska100
Delaware100Alaska100
Maryland100Oklahoma100
New York100Idaho100
Massachusetts100Wyoming100
Hawaii100Utah100
Rhode Island100
Vermont100
DC100

Based on these state win probabilities, the distribution of possible Electoral College outcomes looks like this:

Ultimately, the model suggests that President Obama has a 98.8% probability of winning, at a minimum,
the necessary 270 Electoral Votes he needs in order to win re-election.