You may recall that in the September/October issue of the Washington Monthly, George Washington University political scientist John Sides cited research showing that presidential debates are rarely decisive events, though 1960 and 2000 were probably exceptions.
So we asked Professor Sides to reconsider that judgment after Election Day, given the MSM consensus that the first debate between Barack Obama and Mitt Romney lifted the Republicans very nearly to the presidency.
His web-exclusive answer can be found here. The bottom line is that the Denver debate really didn’t much matter:
[A] few pundits seemed to think that the first debate had shown political science was wrong. But at the end, 2012 largely confirms prior research. Romney gained somewhere between 2-4 points after the first debate, which is in line with previous debate bumps. The 4-point swing is most visible in polling averages, but there is some evidence that it was smaller, maybe in the 1-2 point range. (Part of the swing may have been driven not by the people changing their minds, but by the changing composition of “likely voters,” as Republicans became more enthusiastic and likely to declare themselves likely to vote.)
But no matter the precise size of the swing, the first debate was not the end of the story. In my piece, I noted how the impact of a debate can be overtaken not only by subsequent debates but by subsequent events in the campaign. In 2012, the second and third debates — in which Obama was judged to have “won” by pluralities or majorities of voters — did not clearly shift the polls toward Obama. But they did illustrate how difficult it is for one candidate to run the table and win every debate. More common is that the candidates fight to a draw. The late movement toward Obama, which is visible in the Pollster national average, also suggests how later events can matter. Perhaps in this case it was Hurricane Sandy.
In other words, the game didn’t change; just some of the dynamics and a lot of the spin.