Nyhan explains Birther reversal--sort of

Awhile back I did some tweaking of political scientist Brendan Nyhan over his prediction that the release of President Obama's long form birth certificate would not significantly dent the proportion of Americans who believe Obama was not American-born.

A Washington Post poll showed a big shift in belief as well as a surprising (to me, anyway) number of self-identified Democrats who doubt Obama was born in the United States.

I figured that left Nyhan with some explaining to do.  And, to his credit, Nyhan has stepped up to the plate to do just that:

So why was this correction so effective when others tend to fail? (PDF) The answers aren't entirely clear yet, but here are some initial thoughts. First, the birth certificate's release was an unusually definitive debunking that became a major news event, so there was saturation coverage of some very strong corrective information.

Nyhan's first possible explanation is interesting given that his past "misperception" studies place little weight on the strength of the debunking material.  Indeed, even the supposed misperceptions are often controversial regarding the degree of truth they hold.

Nyhan ought to have considered the strength of the debunking in this case before putting his doubts in print.  It ended up making him look a tad foolish.  He should also have considered that Obama's failure to release the long form certificate when it was apparently in his power to do so did plenty to help fuel the "Birther" movement.  Of course cutting off a major fuel source will affect the level of belief under such conditions.

Nyhan:

Second, no prominent elites on the right contested the validity of the birth certificate, which meant that coverage of its release was almost entirely one-sided.

That fits with my counter-Nyhan argument that the source of contradicting information has much to do with whether we accept a supposedly strong debunking account.  Perhaps it is a failure on my part, but I don't recall Nyhan taking such things into account for purposes of his past research.

Nyhan:

Finally, it's possible that support for the myth was soft because poll respondents didn't really believe it but were using poll questions about Obama's religion and place of birth as a way to express disapproval (as some commentators and pollsters have argued).

Such influences on polling, if they exert an appreciable effect on the results, certainly must make it tough for people like Nyhan to do their research.  How is a researcher to know when people are telling the truth about their beliefs?

Nyhan's three would-be explanations all tend to undercut the conclusions he's drawn from his research.  Will this contradictory information correct his misperceptions?  Was the debunking unambiguous enough to shake his beliefs?