Former poll lover Donald Trump, now trailing in post-convention surveys, has come up with a new theory to explain why he’s not ahead: His supporters are lying to pollsters.

.@realDonaldTrump jokes that he wins because people publicly say they won't vote for him, then get in the booth and say "anyone looking?" — John Roberts (@johnrobertsFox) August 2, 2016

While “people are too embarrassed to admit they support me” may not be an especially winning campaign message, the idea itself isn’t particularly far-fetched. Pollsters recognize something called social desirability bias, when voters are reluctant to tell an interviewer they hold an unpopular position.

The phenomenon has caused real problems for polls in the past. The canonical American example is Tom Bradley, the mayor of Los Angeles and an African American. He narrowly lost the 1982 race for California’s governorship to a white candidate, despite leading in the polls. In the U.K., the “shy Tory” factor left surveys, particularly in the 1990s, seriously underestimating how many conservative voters would turn out on Election Day.

But pollsters for both parties say there is little evidence to suggest that Trump is facing a similar issue.

“It’s possible [that some respondents won’t admit to supporting Trump], but I don’t think so,” said Bill McInturff, a longtime Republican pollster. “For two candidates with unusual negatives, the ballot by sub-group looks pretty traditional for what we’ve been seeing the last few cycles.”

“We won’t be able to say for sure until after Election Day, but it’s very unlikely,” said Mark Mellman, a longtime Democratic pollster. “Most of these kinds of theories don’t hold much water. People claimed primary polls were undercounting the Trump vote and they did not.”

Indeed, if Trump’s poll numbers were suffering from voter embarrassment, we probably would have seen it already. But Trump did not reliably outperform the polls in actual voting during the Republican primaries. As FiveThirtyEight’s Harry Enten noted in May, “Trump did worse than the polling forecast in 19 states; he did better in 15 states. ... Overall, Trump’s percentage of the vote versus the polls is about what you’d expect of the average politician.”

A pollster for Sen. Ted Cruz, Trump’s rival in the primaries, told Politico last month that Cruz’s campaign faced “no challenge accurately measuring Trump voter support” and saw “zero evidence” of a shy Trump effect.

The general election might be different from the primaries. Republican voters reluctantly falling into line with their nominee could be more susceptible to embarrassment.

If so, there would be another way of measuring it: Trump would be doing worse in polls conducted by a live interviewer than in polls conducted online or using automated phone calls, where respondents don’t have to disclose their opinions to real people.

“The best way to see it would be to compare self-administered with live interviewer,” said Anna Greenberg, a Democratic pollster. “The problem is we don’t really have comparable self-administered and live surveys since MOST self-administered are not representative random samples.”

Still, data from HuffPost Pollster’s tracking of the presidential race suggest that support for Trump varies little between live-interviewer surveys and those conducted online or using automated calls.

Natalie Jackson/Huffington Post

Greenberg noted one other way of testing whether Trump is suffering from voter embarrassment. And here too, she said, the phenomenon seems overstated or non-existent.

“I also look at how the Trump vote lines up with partisanship,” she said in an email before the conventions. “In many of the places I’m polling, Trump’s vote is lining up with the percent who call themselves Republican.”

If anything, Greenberg said at the time, it was Hillary Clinton who was “underperforming relative to partisanship.”

Editor’s note: Donald Trump regularly incites political violence and is a serial liar, rampant xenophobe, racist, misogynist and birther who has repeatedly pledged to ban all Muslims ― 1.6 billion members of an entire religion ― from entering the U.S.