When voters lie to pollsters, it’s called the “Bradley Effect,” after Los Angeles Mayor Thomas J. Bradley lost the the 1982 California governor’s race even though he was leading in the pre-election and exit polls.

The dominant theory about how the polls got it wrong is that voters, eager to impress the pollster, claimed they supported Bradley, who would have been the state’s first black governor.

Emerson College Professor Gregory Payne tells Breitbart News that after witnessing the actual Bradley Effect while working on that campaign, he sees the same phenomenon in the 2016 with voters reluctant to tell pollsters they support GOP presidential nominee Donald Trump.

Payne said he knew the polls showed Bradley leading Republican George Deukmejian, but he was personally skeptical.

All through Election Day, exit polls also showed that Bradley had a solid lead, but Deukmejian beat Bradley by less than 100,000 votes, 49 percent to Bradley’s 48 percent.

Payne said there were other factors that helped Deukmejian, such as a referendum on the statewide ballot that would have created a gun registry, which energized gun owners and supporters of gun rights, and the high number of absentee ballots from Orange County. “Some of it might be due to racism or whatever.”

But, there was a real social pressure during the campaign for people to support Bradley, who would have been the first African-American governor of the Golden State, he said.

“People, when you’d ask them if they were going to vote, oftentimes they would say they were going to vote for Bradley or a black candidate so they felt socially acceptable,” he said. “Then when they went behind the curtain, they decided that they didn’t really want to vote for Bradley.”

The professor, who has published on the subject of polling in Behavioral Science magazine and has worked with Emerson’s own Emerson College Polling Society, said the social pressure against supporting Trump is very strong.

“I think with Trump, what you have is you have the opposite,” he said. “Many people are saying to maybe their friends while they’re having a sip of Chardonnay in Washington or Boston, ‘Oh, I would never vote for him, he’s so – not politically correct,’ or whatever, but then they’re going to go and vote for him. Because he’s saying things that they would like to say, but they’re not politically courageous enough to say it and I think that’s the real question in this election.”

There is no denying that Trump has tapped into a real concerns of voters, said the professor, who wrote speeches for Bradley and authored the biography: Tom Bradley: The Impossible Dream.

“Trump is kind of a combination of the gun referendum, because he’s an emotional energy source for people who want to make sure that they’re voicing their concerns about all these issues – immigration, et cetera – but then I think there’s this other piece. They don’t find it to be correct or acceptable to a lot of their friends, but when push comes to shove, they’re going to vote for him.”

Payne is not the only one talking about a “Trump Effect” or struggling to get a handle on secret Trump supporters. In his May 11 column in The New York Times, Thomas B. Edsall quoted Kyle A. Dropp, the executive director of polling for Morning Consult. He’d detected a gap between Trump’s support in online polls and in phone polls, which may speak to the reluctance to admit to supporting Trump.

Trump’s advantage in online polls compared with live telephone polling is eight or nine percentage points among likely voters. This difference, Dropp notes, is driven largely by more educated voters — those who would be most concerned with “social desirability.” These findings suggest that Trump will head into the general election with support from voters who are reluctant to admit their preferences to a live person in a phone survey, but who may well be inclined to cast a ballot for Trump on Election Day.

The social pressure in Silicon Valley to not back Trump is strong, according to a July 15 article in Business Insider. The website interviewed a Silicon Valley software engineer, who described the pressure using the assumed name “Jake.”

Now Jake tries to keep his Trump support a secret. Despite supporting the candidate both financially and in person, Jake believes his entire career could be at risk if his name were publicly linked to Trump. Business Insider agreed to interview him over email on conditions of anonymity and that we change his first name in the story. “In Silicon Valley, because of the high prevalence of highly smart people, there is a general stereotype that voting Republican is for dummies,” he says. “So many people see considering supporting Republican candidates, particularly Donald Trump, anathema to the whole Silicon Valley ethos that values smarts and merit.”

There is a similar phenomenon in the United Kingdom with what is called the “Shy Tory,” which is played out in predictions the 2015 parliamentary election was a dead-heat, only to see the Conservative Party beat the Labour Party by 6 percentage points. Most recently, in the referendum on the United Kingdom’s staying in the European Union, all pollsters had the “Remain” side winning in a climate, where all the celebrities and the political and business leaders all endorsing Remain. Of course, “Leave” won.

In the 2016 presidential campaign, both Hillary Clinton at 42 percent and Trump at 37 percent are trailing in the polls, each by roughly 10 percentage points below where the nominees from their own party finished in the 2012 race. The missing 20 percent is hiding with Libertarian Gary Johnson at 9 percent and Green Party nominee Dr. Jill Stein at 3 percent and the undecided at 8 percent.

Over time in a presidential campaign, it is normal for third-party candidates, not tied to a region, to lose support as the election draws closer and assuming the undecided come to a decision, there are still millions of votes in play.

Now, the question is how many of those voters are cloaking their support for Trump claiming to be undecided or supporting someone else?