Is the Generic Ballot Underestimating the Democrats?
Nate Silver wrote an interesting column this week, arguing that the generic ballot might be underestimating the Democratic position right now. Silver writes:
In the last couple of posts on our House forecasts, I’ve noted that the generic Congressional ballot tends to show worse results for Democrats than other indicators like polls of individual House races. The generic ballot, as of last week, pointed toward a Republican lead of 7 or 8 percentage points among likely voters, according to our estimates. Local polls are a little bit less straightforward to read because you have to make a lot of adjustments for polls that are (i) partisan, (ii) bad, or (iii) both. But in general — while there is a lot of variance from district to district — the local polls seem to point toward a House vote that would be about evenly divided.
Color me a skeptic. Historically, the generic ballot has overestimated, not underestimated, the Democratic position. I’m open to such a change as a theoretical possibility, but there is a significant evidentiary burden to be met. And I don’t think Silver’s analysis meets it. For starters, any analysis that uses House polls is going to be problematic for all the reasons that Silver cites. Beyond that, Senate polling is certainly consistent with an R+7 national year, and you don't find John Dingell under 50 percent in anything short of a GOP tidal wave.
Yet Silver uses the polls from the conservative American Action Forum (AAF) to make the case that the generic ballot is suddenly tilted toward the GOP. The AAF has been polling Democratic-held districts and asking voters for their generic preferences (Republican or Democrat) as well as their preferences for specific candidates. Silver notes that actual Democratic candidates do better than the generic Democrat in the AAF polls, and from this he concludes that such a trend might be in play nationwide.
Yet the AAF poll is a bad data set to make the claim that Silver is making. The reason is that an unusually high percentage of respondents to the AAF answered “Depends.” The result is that the AAF generic ballot polls have a much larger undecided/depends bloc than the national polls. The average of the American Action Forum House polls shows a whopping 28 percent of respondents claiming either they are undecided or their vote depends on the candidates. Compare that to the 12.1 percent undecided in the RealClearPolitics generic ballot average.
This is a problem for Silver's conclusion. There is something unique about the AAF methodology, something that pushed an unusually large number of respondents to an uncertain position. I don’t know what the reason is, but frankly it doesn’t matter here. What matters is that there is a difference between the AAF generic ballot polls and the national generic ballot polls. That’s a problem for Silver because he is using the AAF polls to make a point about the national numbers, which means he is basically comparing apples to oranges.
There’s more. Here is how Silver explains the difference in generic versus actual Democratic support in the AAF polls:
Still, the notion that specific Democratic candidates do slightly better than generic ones would square with what we’re seeing elsewhere in the data. It also arguably squares with the respective strategies of the two parties, as Republicans are generally trying to nationalize the race, while Democrats — lacking much in the way of a coherent national message — are trying to localize it…