So far, four five six pollsters have released national surveys using samples taken after the end of the Democratic National Convention, and have data from the post-RNC period. The median swing is a 7.0 ± 1.1 2.0 2.1 % (± estimated SEM) move toward Hillary Clinton.
Here are this year’s bounces, added to the previous graph.
Individual polls:
| Pollster | Pre-DNC | Post-DNC | Swing toward… |
|---|---|---|---|
| Raba | Clinton +5% | Clinton +15% | Clinton 10% |
| PPP* | Clinton +4% | Clinton +5% | Clinton 1% |
| Morning Consult | Trump +4% | Clinton +3% | Clinton 7% |
| CBS | Tied | Clinton +7% | Clinton 7% |
| CNN | Trump +3% | Clinton +9% | Clinton 12% |
| YouGov (4-way) | Clinton +2% | Clinton +5% | Clinton 3% |
The Pre-DNC measurement from PPP was taken in June, predating both conventions. The resulting swing therefore represents a combination of the Republican and Democratic conventions. However, since the median post-Republican convention swing was only 1 point, it was still informative and I included it. Since you can do medians in your head, you can see that this does not make a difference given the current data set.
YouGov leads its report with the 4-way (Clinton v. Trump v. Johnson v. Stein) result, showing a 3-point swing toward Clinton. The 2-way result shows a 2-point swing in the opposite direction, toward Trump. Again, the median is the same no matter which one of these is used. However, the error bar is affected slightly.
I have seen some sniffy comments in the news that Hillary Clinton’s post-convention bounce is smaller than Bill Clinton’s bounce in 1992. However, by current standards, Hillary Clinton’s bounce is large. As I wrote the other day, post-convention bounces have been small for presidential elections since 1996, which I suggest is a symptom of political polarization: voters get entrenched in their support.
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