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Could Bradley Effect Change November Election?

SAN FRANCISCO (CBS 5) ― In 1982, polls showed Los Angeles Mayor Tom Bradley virtually assured of victory in the governor's race, but he lost. Since then, when polls say one thing and election results say another, it's been called the Bradley Effect.

Political Consultant Don Solem explains: "It's not so much they're afraid to say it as they think it might be taken the wrong way."

Solem said the Bradley Effect is also known as social desirability bias.

"The bias is for what's acceptable and you tend to understate your opposition to what is perceived to be acceptable," Solem said.

Social desirability bias presents itself in all kinds of questions.

Ask yourself, how honest would you be answering questions such as:
-How much do you drink?
-How often do you have sex?
-Have you ever been convicted of a crime?
-How much money do you make?

Walnut Creek resident Carol Ferrara came up with another: "When your dentist asks do you floss? Oh yes."

One issue on the November ballot that may involve social desirability bias is Proposition 8, which would make marriages in California only between one man and one woman.

Some voters might not want to tell pollsters they're against same-sex marriage because, "they think it'll be misinterpreted like they're against all homosexuals or somehow they won't be viewed as believing in equality and so on," Solem said.

Then there's presidential candidate Barack Obama. He's black, just as Bradley was. His election would be a first for the United States.

No matter the reason someone may have to vote against Obama, a no vote could be interpreted by some as a racist vote. Who wants that?

"You don't want to be branded that," Solem said. "There's a stigma attached to it, you realize that that's not acceptable."

San Francisco resident Mark Jen understands the Bradley effect. "I guess I feel that's pretty normal and whoever's running the poll should account for that statistical anomaly," he said.

Solem said social desirability bias skews polls by five or six percentage points, at most; it's not a huge factor.

But apparently wanting to follow social norms is.

"I do think that some people would just give the right answer," Ferrara said. "I don't think that I would unless I was embarrassed about my answer and I just didn't want to tell you."

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