Why poll numbers skewed: Race effect? - Daniel Libit

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Why poll numbers skewed: Race effect?

By DANIEL LIBIT | 5/16/08 4:55 AM EST

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Tom Bradley with his wife, Ethel, left, and daughter, Lorraine; June 1986

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.

Photo: AP

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.

“We know that biracial elections have been difficult for pollsters,” says Andrew Kohut, president of the Pew Research Center. “Race continues to be an issue for Obama, and to the extent race is an issue, race will be an issue in polling.”

The 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. It resurfaced in the 1989 Virginia governor’s election when L. Douglas Wilder, an African-American, barely squeaked by his Republican opponent despite polling that reflected a commanding double-digit lead for Wilder heading into Election Day.

Some observers saw evidence of the Bradley effect right out of the gate this year in New Hampshire. While surveys were close to the mark on the Republican side, polls for the Democratic primary showed Obama with a steady lead over Hillary Rodham Clinton in a contest he eventually lost 39 percent to 36 percent. The average margin of polls taken up until a day before the election projected an 8-point Obama lead.

Exit polls showed that Clinton narrowly edged Obama among voters who made up their decision on Election Day, suggesting that the discrepancies between pre-election polls and the actual vote couldn’t be explained away by a last-minute flood of Clinton support.

Others saw the Bradley effect at work in the Rhode Island primary in early March, where Clinton’s 58 percent to 40 percent victory was also notably wider than expected — the RealClearPolitics polling average showed a margin of 9.7 percent.

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.

Yet for all the worry surrounding the Bradley effect, there is still considerable debate over whether it is a significant cause of polling error — or even a real one at that.

Skeptics point to a number of other elections featuring black candidates where the phenomenon hasn’t surfaced, the most recent of which is the 2006 Tennessee Senate race between Democrat Harold Ford and Republican Bob Corker. In that election, polls showed Corker with a 12-point lead over the African-American Ford just three days out. Ultimately, though, the election margin proved razor thin.

“I expected no more questions about Bradley effect after the Ford race,” says Tom Lee, a Nashville attorney who served as a top adviser to Ford in the race. Lee says that the campaign’s internal poll numbers were accurate the whole way through but that other polls failed to screen out unlikely voters, who in Tennessee tend to be more conservative.

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Replies: 482

Fedaykinn

Party: Independent

Reply #1

Date: May. 16, 2008 - 5:27 AM EST

The sad part is that the media perpetuates much of this effect by endlessly pointing out racial differences in certain states exit polls or remembering cases like Bradley.

The younger generations of Americans (45 and younger) are very rarely racist or sexist... and it is about time the US gets a minority to be president (or a woman for that matter) so we can forget about this stupidity once and for all.

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