5 February 2008
Another Tuesday, another primary election or twenty, and another opportunity for things to go wrong with pre-election polls. The super Tuesday states, which had not seen much attention from pollsters earlier in January, have seen a deluge of polls released in the last week, nicely summarized at the Mystery Pollster blog. As Mark Blumenthal's recent post points out, "Somebody's gonna be wrong". The amount of dispersion present in the recent polls on both sides of the election exhibit is far more than can be accounted for by sampling variability. There are always house effects present in any polling context, but this borders on the ridiculuous. Unlike New Hampshire, no matter how the results turn out (barring a possible McCain collapse), we probably won't see as great a hue and cry about the pollsters this time because their pre-election predictions are all over the map.
Speaking of New Hampshire, Adam Berinsky from MIT e-mailed a few weeks ago to point to several studies that do look at errors in polling when a black candidate is on the ballot. These include Voting Hopes Or Fears?: White Voters, Black Candidates & Racial Politics by Keith Reeves, "Race-of-Interviewer Effects in a Preelection Poll: Virginia 1989" by Finkel, Guterbock, and Borg, and last but not least, Berinsky's Silent Voices: Public Opinion and Political Participation in America. This just goes to show me that a quick Google Scholar search on "Bradley effect" misses a lot of good stuff. We'll see if there is more evidence of such an effect tonight, but it is worth noting that in South Carolina things went the other way; Obama did much better than projected by the pre-election polls. Since they didn't get the outcome wrong, however, the pollsters didn't get nearly as much grief as they did after New Hampshire.