FiveThirtyEight.com: Bradley Effect? Or Elephant Effect?

FiveThirtyEight.com

Bradley Effect? Or Elephant Effect?

I have received quite a number of requests for comment on the article published by Republican consultant Bill Greener at Salon.com. The article purports to find evidence of a “Bradley Effect” in Senate and Gubernatorial Elections in involving black candidates in 2006. 

So, I’ll comment on it.

Problem #1: Greener cites data from four races: the Tennessee and Maryland senate races, and the Massachusetts and Ohio governor’s races. Greene, however, ignores a fifth race, the Pennsylvania governor’s race, in which a white Democrat, Ed Rendell, competed against a black Republican, Lynn Swann.

Rendell defeated Swann in this race. However, Rendell’s margin of victory was no larger than that predicted by the polls (in fact, it was incrementally smaller). Greener completely ignores this race.

(There was actually a sixth race involving a black candidate, that being in Mississippi, where Trent Lott won re-election to the Senate over Erik Fleming. However, there was essentially no polling of this race, so it isn’t useful to us.)

Problem #2: Greener cherry-picks his data in literally every race. He isn’t even subtle about it. Here is a good example:

How about Tennessee, where black Democrat Harold Ford was up against white Republican Bob Corker for Republican Bill Frist’s old U.S. Senate seat? Harold Ford did slightly better than Steele and Blackwell. The day before the election, he was within a point of Corker, 47 to 48 with 5 percent undecided, according to OnPoint Polling. On Nov. 7, Corker got 50.7 percent of the vote, Ford got 48 and an assortment of independents took 1.3 percent. Ford was able to pick up one out of every five undecided voters.

OnPoint was the only polling firm to show the Tennessee race within 1 point on the eve of the election. Meanwhile, Gallup showed a 3-point lead for Corker, Rasmussen showed a 4-point lead for Corker, SurveyUSA and Pollmetrix showed 5-point leads, and Mason-Dixon showed a 12-point lead. Corker eventually won by 2.7 points, smaller than the margin predicted by all firms butOnPoint.

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