Here is an example of evidence, though still only a single case. In a New York City mayoral primary between David Dinkins and Ed Koch, the Dinkins led by 0 to 5% in the weeks before the election, but ended up winning by 8%. See pages 487 and 490 of this PDF.

Actually, I wasn’t taking a position, just asking a question. Having lived through the Wilder election, I can tell you it certainly seemed like something strange was going on. You have a lt. gov. in an overwhelmingly popular and successful administration running for gov. He never trails in any published poll. Leads by more than MOE in most of them. Is called the winner early on election night by all three networks based on exit polling that predicts a 10-point win. Election ends up in re-count and final margin is ~6,500 votes.

I suppose that’s all anecdotal in a way, and I don’t really know where to track down the internals of those polls almost twenty years later. But it’s something I’d think should be studied rather than dismissed.

However, you are guilty of selectively accepting one piece of evidence that agrees with your position. This is called biased assimilation. There have been African-American candidates besides Wilder. What happened in those cases? Is there a systematic survey of the evidence?

A contrary bit of evidence is that Obama is said to have outperformed polls in his primary contests. Does this suggest that there is an anti-Bradley effect? Nate Silver has suggested as much, and is now assigning undecided African-American voters to Obama. I consider this to be an error as well.

To reiterate, I am looking for evidence of an unbiased nature. I am certainly interested in getting to the bottom of the subject. I am open to the whole range of options – Bradley, no effect, anti-Bradley. But the existing lore does not meet my standard of proof.

That having been said, if you have articles with actual data to send me, including documentation of the Wilder case, by all means do so.

In fact, in the 2008 primaries, Southern states saw a “Reverse Bradley Effect”. We don’t yet know if it will carry over to the general though.

If you dispute the existence of the Bradley effect, what is your take on the 1989 gubernatorial election in Virginia? Doug Wilder had a 4-15 point lead in all the pre-election polls, but won by >0.5%.

Richard/BirdLives: your points are interesting but speculative. I especially contest the size and even the existence of the “Bradley effect.” If you have some actual documentation of this phenomenon that is not based on exit polls, I promise to make use of it in a future posting.