The PollyVote published highly accurate popular vote forecasts for the three U.S. presidential elections from 2004 to 2012.
The 2012 PollyVote was launched in January 2011 and forecast a victory for President Obama over the 22 months that it was making daily forecasts. On Election Eve, it predicted that Obama would receive 51.0% of the popular two-party vote, an error of 0.9 percentage points.
PollyVote’s long-term forecasts were even more accurate. From January 1, 2012 until Election Day, the PollyVote forecast missed the final election results by only 0.3 percentage points.
The forecast was also substantially more accurate than the closely watched forecasts at FiveThirtyEight.com. That is, relying on the PollyVote rather than on FiveThirtyEight, across the period when forecasts from both methods were available, would have reduced forecast error by 42% when predicting the popular vote.
The 2008 PollyVote was launched in August 2007 and forecast a victory for Barack Obama over the 14 months that it was making daily forecasts. On Election Eve, it predicted that Obama would receive 53.0% of the popular two-party vote, an error of 0.7 percentage points.
The 2004 PollyVote was launched in March 2004 and forecast a victory for President Bush over the 8 months that it was making forecasts. The final forecast published on the morning of the election predicted that President would receive 51.5% of the popular two-party vote, an error of 0.3 percentage points.
We also conducted an ex post analysis by adding the three elections from 1992 to 2000 to the sample in order to provide additional evidence. Across the last 100 days before each of the six elections from 1992 to 2012, the PollyVote provided more accurate forecasts than each of its component methods. Error reductions were large, in particular compared to polls, for which the error was reduced by more than half.