August 31, 2012
WonkBlog - washingtonpost.com
by Dylan Matthews
"Forecasting the Election: Most models say Obama will win. But not all.”
Study: “History and Primary: The Obama Re-election.”
Who did it: Helmut Norpoth and Michael Bednarczuk (SUNY, Stony Brook University).
The variables: Uniquely among the studies here, Norpoth and Bednarczuk do not include any economic variables. Instead, they simply use the share each major party candidate got of the primary vote in the New Hampshire primary. To account for presidents who run unopposed, they set a maximum possible vote share of 65 percent, and a minimum possible share of 35 percent. That is, if a candidate got between 65 and 100 percent of the vote, that’d be inputted as 65 percent, and if a candidate got between 0 and 35 percent of the vote, that’d be inputted as 35 percent.
How well it does: The model has an adjusted R-squared value of 0.89. In plain English, that means that it explains about 89 percent of variation in party vote shares between presidential elections.
What it predicts: The model forecasts Obama will get 53.2 percent of the two-party vote and Romney will get 46.8 percent. This gives Obama an 88 percent chance of winning.