In my debate with Bryan Caplan (vid here), his position was a strong audience favorite before, and less so after. When I heard that Tyler Cowen just had the same experience in his debate, I suggested to the lunch crowd that maybe in general debates move audiences toward a 50/50 opinion split. The org that sponsored Tyler’s debate has done 27 of them so far, so I typed that data in and it is easy to see that their data supports my hypothesis:
The initially disfavored side almost always gains a lot (vs. the zero gain red line). Alex Tabarrok weighs theories to explain this; my guess is that hearing half of a long hi-profile argument time devoted to something makes it seem more equally plausible.
Here is the analogous before/after chart for the favorite side: