More than 90 percent of Americans would be willing to vote for a well-qualified woman for president, according to a Gallup poll that posed the question last year, yet 22 percent of respondents said that they thought “most of the people they know” would not “vote for a presidential candidate who is a woman” when asked in a YouGov poll the same year. Why the large gap between what people say they would do and what they think other people would do?

One explanation is that when asked directly about their opinions, people might try to offer a more socially acceptable answer. When asked about others’ opinions, people may indirectly reveal their own true feelings. Research has consistently found that respondents lie on surveys about their attitudes on sensitive topics, such as racial or gender attitudes, out of fear of being seen as racist or sexist. This propensity to conceal one’s true attitudes in the face of social pressure is known to researchers as “social desirability bias.”

To get around this problem, social scientists sometimes divide survey respondents into two groups and ask them both to identify how many opinions on a list they agree with (but not which opinions). One group’s list has a socially undesirable opinion added. By calculating the difference between the groups, researchers can determine how many people hold the undesirable opinion.

This method has been used to measure racism, attitudes about immigrants, and perhaps most importantly for this election, support for a female president. In one 2008 study researchers asked people how many statements on a list made them “angry or upset.” The researchers found that 26 percent of respondents were angry at the idea of a woman serving as president, 18 percent more than people who said that they would not vote for a well-qualified female candidate when directly asked in last year’s Gallup poll and closer to the 22 percent figure of people who indicated that most people they knew would not vote for a female candidate for president in the YouGov poll.

Does this mean that polls showing Clinton leading Trump should be held suspect? Well, not exactly. There are many other reasons that some voters might oppose Clinton other than her gender, so social pressure to support a woman is probably not a major factor. In fact, political scientists Christopher Stout and Reuben Kline have found evidence that polls on U.S. Senate and gubernatorial races consistently underestimate support for female candidates relative to their actual vote shares. The chart below, built from their data, demonstrates this finding. Points above and to the left of the reference line are elections in which the female candidates outperformed their pre-election polling numbers.

Stout and Kline theorize that this discrepancy between polling and election results was due to respondents’ not wanting to appear progressive or feminist on gender issues. That phenomenon is particularly evident in states with a conservative voting record on gender issues and in those with lower percentages of women in the labor force. Another explanation for this finding, suggested by Kelly Dittmar of the Center for American Women and Politics, is that the polls could be capturing people’s pre-election preferences for male candidates, but on Election Day, people tend to vote along party lines.

For this election, the research suggests that there may be a ceiling on support for Clinton based on her gender, but that doesn’t necessarily mean that polls are overestimating her support. If anything, the opposite may be true. Even though gender will play some role throughout the election in both candidates’ talking points, there are other factors that will probably play a far more influential role in this election than the gender of the first female nominee of a major party.