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Handicapping the House: Part II

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Yesterday, our Slate update shifted to a district-by-district focus on races for the U.S. House. Our initial tally shows Democrats right on the edge of statistically meaningful leads in enough districts to take control of the House, and Democratic challengers running within the margin of error in many more. While we are working to creating a more comprehensive scorecard, I want to say a bit more about how our initial count given the limitations of the data.

For now we are focusing on non-partisan surveys conducted since late August (which allows inclusion of the first wave of Majority Watch surveys conducted August 27-29). We have excluded the surveys sponsored by campaigns or the party committees (including those conducted by my firm).

Looking at the survey averages in districts with two or more polls available, we see Democrats leading beyond the margin of error in ten districts currently held by Republicans (the number of surveys analyzed is included in parentheses):

In addition, we see statistically significant Democratic leads in four more districts held by Republicans surveyed only once by non-partisans since the summer (all four were polled by the Majority Watch project):

[Note: We inadvertently omitted Ohio-18 and North Carolina-08 from last night's initial Slate update].

Perhaps more troubling for Republicans is that we see no Republican leading in any district currently held by a Democrat. Moreover, of the 23 Republican held seats currently rated as "toss-ups" by the Cook Political Report, Democrats lead by significant margins in 9, Republicans leading in none just one (Minnesota-02).** The remaining 13 Republican "toss-up" seats look too close to call based on available data. And that says nothing of the 31 Republican seats that Cook rates at "lean" or "likely" Republican, where public polling is scarcer still.

Of course, readers should remember the limitations of these data. Any one poll can produce an odd or contradictory result and many of the polls conducted in September may already be stale. Consider, for example, Iowa's 1st District (an open seat currently held by Republican Jim Nussle). A Majority Watch poll in late August showed the Democratic candidate Bruce Braley leading Republican Mike Whalen by thirteen points (54% to 41%). Two weeks later, a DeMoines Register/Selzer poll conducted two weeks later had Braley ahead by seven (44% to 37%). Then a Zogby poll at the end of September showed Braley trailing by thirteen (34% to 47%). And finally, a poll conducted by my firm last week for the Democratic Congressional Campaign Committee had Braley ahead by 10 (48% to 37%). So over the course of six weeks, polls in one district show everything from a 13 point Democratic lead to a 13 point deficit with undecided percentages ranging from 5% to 19%. These differences are far beyond sampling error and almost certainly the result of differences in pollster methodology. And that's just one district.

Again, we are working on creating a House summary scorecard for Pollster.com, but it will be limited by both the relatively small number of public polls and their inevitable conflicts.

**Correction: I wrongly included MN-02 (rather than MN-06) among the list of seats rated a "toss-up" by the Cook Political Report. Four polls in MN-06 since mid-September give Democrat-Farm-Labor candidate Patty Wetterling an average lead of one percentage point (45.7% to 44.7%) over Republican Michelle Bachman. Apologies for the error.