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Daily Breakdown: Romney's Bounce Levels Off, But Will It Last?

After lurching in Romney’s direction on Saturday, Gallup, Reuters/Ipsos, and Rasmussen all held steady, perhaps indicating that Romney’s bounce was leveling off. 

Two big questions:

1) How big was Romney’s bounce? It still make sense to refrain from confidently judging the size of Romney’s post-debate bounce until a representative set of pollsters weigh-in, since, so far, only one live interview pollster has conducted a survey entirely after the first presidential debate. Instead, automated firms that don’t poll cell phone voters are responsible for a disproportionate share of polls.

That said, if we were to judge the size of Romney’s bounce based on the available information, it would probably suggest a bounce somewhere just north of 3 points. Start with a broader comparison of the polls with their pre-convention counterparts, which shows Romney gaining about 3.5 points:

But as mentioned on Saturday, reconsidering the Rasmussen polls in terms of their pre-DNC averages makes Romney's bounce look a little smaller. Broadening this perspective to the other polls points toward a three point gain, especially when considering the Rasmussen and the Gallup approval tracker. Both samples now entirely consist of interviews conducted after the debates and when compared to their post-DNC averages, and both showed Romney gaining three points compared to their post-DNC averages, a finding relatively consistent with Nate Silver’s analysis relying on post-DNC averages last night (although his method may understate Romney’s bounce in Gallup, since their approval tracker suggests that Obama fared very well in Gallup's pre-debate samples).

Another reason to believe that the 3.5 point number is too high is the Seltzer/Denver University survey, which showed Obama leading by 4 points in Colorado. Seltzer did not conduct a post-DNC poll of Colorado, so the poll does not show up in the "Romney's bounce" chart. But Seltzer's poll of the country and lowa showed Obama leading by 6 and 4 points, respectively. Since Colorado tilted slightly toward Romney compared to the country in post-DNC polls, the Seltzer poll doesn't necessarily point toward any movement in Romney's direction at all. Even though the Seltzer poll doesn't factor into the 3.5 point number above, it should be interpreted as a strong reason to take the under, especially since Seltzer is highly regarded and it represents the only live interview survey conducted entirely after the debates. 

2) Will Romney's bounce last? The evolution of the post-debate tracking polls suggests that Romney’s post-debate bounce might be fleeting, or at least smaller than the polls conducted immediately after the debates. Before diving in, remember that tracking polls change on a rolling basis: when the newest day of interviews is added to the tracker, the oldest day is dropped. With that in mind, consider that most of the movement in the trackers occurred on Saturday, which indicates that the interviews conducted on days other than Friday were relatively consistent with the dropped samples from before the debates. PPP reported a similar tendency in their polls of Wisconsin and Virginia. Of course, it wouldn't be a surprise if this turned out to be noise, but it raises the possibility that Romney's bounce might be short-lived.