Black candidates and polling

Important article from Politico:

A phenomenon, known in the trade as 'social desirability bias,' draws its name from Tom Bradley, the former black mayor of Los Angeles who lost the 1982 California gubernatorial election despite leading in final day pre-election polls.

Further,

As the nation’s pollsters convene this weekend in New Orleans at the annual conference of the American Association for Public Opinion Research, one topic will be the subject of lively debate — the so-called “Bradley effect.”

The Bradley effect, which refers to the propensity of white poll respondents to overstate their support for a black candidate, isn’t the only issue that pollsters, statisticians and academics will discuss and dispute. But it may be one of the most consequential since it stands to significantly skew pre-election poll results in an election where it seems increasingly likely that Barack Obama will emerge as the Democratic party’s presidential nominee.

However,

In states with larger black populations, such as North Carolina and South Carolina — where polls had Obama leading by 9 points, when he actually won by 28 — there’s even been talk of a reverse-Bradley effect, whereby Obama’s support was underreported in pre-election polls.