“Gallup’s polling and modeling predicted a wave election for the Republicans in the House, projecting 60 or more seats gained by the GOP. This is what occurred.”
That’s what the Gallup Poll had to say on the day after the 2010 midterm election about the accuracy of their final pre-election poll in which they showed a generic Republican leading a generic Democrat by a 15 point margin. But is it true?
The answer is a loud and clear, no. Yes, it was a big Republican wave but the actual popular vote margin was about 7 points, not 15 points. Based on the normal relationship between votes and seats in House elections, a 7 point margin would be expected to result in about 240 Republican seats, which is almost exactly the number Republicans will end up with. Right now it looks like the final number will be 243. That’s a pickup of 64 seats which is huge. But a 15 point Republican margin would be expected to result in about 272 Republican seats in the House, a pickup of over 90 seats. That would not just be huge, it would be totally outside the realm of anything experienced in American politics since the 1920s.
Strangely, in their election post-mortem Gallup didn’t even mention their actual final poll result, something they typically like to brag about. That’s probably because their final poll missed the actual popular vote by the biggest margin of any major polling organization, and by the biggest margin in the history of the Gallup Poll. So no, Gallup did not get it right and they should be trying to figure out how their generic ballot poll went so badly wrong, not pretending that everything was just fine. The first step to correcting one’s errors is admitting that you were wrong. We have yet to see Gallup do that.