I don’t usually like to comment on individual polls. Most of the time, when a poll produces an “unusual” result, it simply reflects random noise and the best advice is to wait for the next edition of the poll to come along, when more often than not it will revert to its previous position.
The poll stealing the headlines this morning is from Gallup, and for good reason: it gives the Republicans a whopping 10-point lead on the generic ballot. This is, in fact, a record for the Republicans: Gallup has been conducting this survey for almost 70 years, and Republicans have never managed to have quite that large of an edge before.
The poll is probably an outlier of sorts, by which I mean that if you were to take the exact same survey and put it into the field again — but interview 1,450 different registered voters, instead of the ones Gallup surveyed — you would most likely not find the G.O.P. with a 10-point advantage. This week’s generic ballot survey by Rasmussen Reports actually bounced back toward the Democrats somewhat (although still showing them with a 6-point deficit); polling averages have them trailing by around 5 points instead; and there was no specific news event last week that would have warranted such a large shift in voter preferences.
Still, even if the poll is an outlier, that doesn’t mean it should simply be dismissed. Instead, the question is: an outlier relative to what? If the Democrats’ true deficit on the generic ballot were 5 points, it would not be all that unusual to have a poll now and then that showed them trailing by 10 points instead, nor would it be so strange for a couple of polls to show the race about tied. Indeed, that seems to be about where the generic ballot sits now. No non-Internet survey has shown the Democrats with a lead larger than 1 point on the generic ballot for over a month now, whereas their worst results of late seem to put them in the range of 10 points to 11 points behind.
This is not the situation the Democrats faced earlier this summer, when the generic ballot was closer to even. Back then, a 5-point Republican lead on the generic ballot would have been pretty big news; now, it seems to be the new normal. I don’t say this cavalierly: FiveThirtyEight tracks the generic ballot pretty obsessively, as it’s used in several ways in our forecasting models, and the Democrats’ numbers have almost certainly undergone some further deterioration over the past few weeks.
Making matters worse still for Democrats, Gallup’s survey — and some other generic ballot polls — are still polling registered rather than likely voters, whereas its polls of likely voters are generally more reliable in midterm elections. At FiveThirtyEight, we’ve found that the gap between registered and likely voter polls this year is about 4 points in the Republicans’ favor — so a 10-point lead in a registered voter poll is the equivalent of about 14 points on a likely-voter basis. Thus, even if this particular Gallup survey was an outlier, it’s not unlikely that we’ll begin to see some 8-, 9- and 10-point leads for Republicans in this poll somewhat routinely once Gallup switches over to a likely voter model at some point after Labor Day — unless Democrats do something to get the momentum back.
The “good news” for the Democrats is that the generic ballot almost certainly isn’t the only metric you should look at when forecasting midterm elections, and the other salient statistical indicators, while poor for Democrats, are not quite this poor. More on that when we release our House model, which is coming soon.