 |
| Image on the left is courtesy of Alaskans For Begich TV ad, and highlights the wealthy, mega-donors Koch Brothers support of Republican candidates. Image on the right comes from an anti-Obamacare ad sponsored by Generation Opportunity. |
Glancing at the current HuffPollster and RCP polling averages, Democrats and Republicans are essentially tied on the generic House ballot question. The former finds Republicans ahead by less than half-a-percentage point, while the latter finds them down by a roughly equal margin. But don't expect the same polling dynamic that exits today to be present on election day - at least not if past generic House ballot polling dating back to 1970 has anything to do with it. And further, I'd caution against relying too much on the surveys taken in the final week before the election, too, as they've been pretty hit-or-miss themselves.
Hundreds of generic ballot surveys taken over the last 45 years and eleven midterms finds polls conducted in the Spring of an election year (April, May, and June) have overstated the eventual Democratic margin in nine of them, or 82% of the time (including the last five midterms in a row). Surveys taken in the final week(s) of a campaign are no exception, understating the Republican margin in eight of eleven elections. Consider the tables below, the first of which provides polling data in the spring of each midterm since 1970 compared to the final result, the second of which compares polling data taken in the final week(s) of the campaign with the actual result.
 |
| Polling data pre-2006 was provided by the Roper Center's IPOLL databank. * Indicates the cutoff date for polls to be included in the average was TWO weeks prior to the actual election day. ** Indicates the cutoff date for polls to be included in the average was THREE weeks prior to the actual election day. Dates were only altered if necessary to obtain a large enough sample to average. |
Surveys conducted in the Spring of the last eleven midterm elections tended to overstate the eventual Democratic margin over Republicans by an average of five net points. Looking at specific elections, such as 2010, you can see Republicans were polling an average 43% in the Spring of that year, though they eventually won 51% of the popular vote. Democrats, meanwhile, were polling an average of 42% that Spring, and wound up with 45% that November. The Republican advantage over Democrats grew from just one point in April, May, and June, to six points in November.
