There probably aren't actually masses of secret Donald Trump voters who have been too shy or embarrassed to truthfully tell pollsters who they are voting for, a study by Politico/Morning Consult found. This appears to contradict the claim by Trump and his campaign manager, the Republican pollster Kellyanne Conway, that reported poll numbers don't accurately reflect the support of Trump due to interviewees feeling uncomfortable telling a human pollster they back the controversial candidate.
The study looked at how voters responded in interviews over the phone versus interviews online, which offer a little more anonymity since they don't involve speaking directly to another person. The difference between the two versions of polling was only slight, and not statistically significant.
"In the primaries, we conducted a study that sought to get at why Donald Trump was performing better in online surveys than on telephone polls," Morning Consult co-founder and Chief Research Officer Kyle Dropp told Politico. "The study showed that a polling mode effect called 'social desirability bias,' — respondents didn’t want to tell a live interviewer they were voting for Trump — was at play. Our new study to assess the general election shows that not to be the case overall, although there are likely still small pockets of shy Trump voters."
You can read more about how researchers ruled out social desirability bias in their study at Politico.