Our yen for “yes” or “no” answers sometimes clouds our understanding – in this case, of presidential debates. Observers seem wedded to saying either “Yes, debates do have an impact” or “No, they don’t.” Reality is more complicated.

A Gallup review “reveal[s] few instances in which the debates may have had a substantive impact on election outcomes – public preferences moved quite a bit around the debates, but the debates did not appear to alter the likely outcome.” Of course, one reason debates have had minimal impact on outcomes is that few presidential races are close. Over half the elections since 1960 have been decided by margins of over 7 points. Altering those outcomes would have required debates to create huge swings. Only five elections were decided by margins of less than 4 points.

Those 4 points are relevant because, using Gallup’s data, that’s the average change in the margin pre- and post-debate. Of course, Gallup’s aren’t the only polls conducted, and we know those polls often provide divergent data. A more comprehensive analysis by Professors Robert Erikson and Christopher Wlezien found that “Debates seem to make at least a bit of difference,” though “any claims about debate effects