The polls in the presidential election between Democrat Hillary Clinton are Republican Donald Trump are currently tightening after weeks of trump lagging behind, but the question many Trump supporters have of whether trump' true level of support is consistently underrepresented by polls is worth examining. The theory is, called the Shy Tory Theory, is borrowed from recent British elections.
The Shy Tory Theory is the idea people polled may be too embarrassed to admit to a pollster they are going to vote for the conservative party even though they will ultimately cast their ballot for the conservatives. The Tories are the conservative party in the United Kingdom. As with the Republican Party in the United states, the media and entertainment industries paint the Tories as ignorant and intolerant in comparison with the “correct” way to vote—for the liberal alternative. So conservative keep their political leanings a secret to avoid the negative stigma. This is supposedly the explanation to why the Tories were lagging behind in the polls leading up to the last general election, but wound up winning handily.
It pays to mention before applying the Shy Tory Theory to the American presidential election bad polling in the United Kingdom is the more likely culprit for surprise election results than closeted Tory voters. Polls also failed to predict the successful Brexit back in June. Since then, the methodology of polling has comes under scrutiny rather than the honesty of respondents.
With good reason. There are three arguments against the Shy Tory Theory impacting trump's poll numbers. One, Trump voters are not generally shy about their support for him. They may certainly be some who are hiding their support in order to keep the peace among friends and family, but most likely not a significant number. Two, it is doubtful a trump supporter would not admit it to a pollster in private over the phone. This is true even for those who will not admit their Trump support to family and friends. Finally, the Bradley Effect, a political science theory stating respondents polled will say they are voting for a black candidate to avoid accusations of racism when they have no intention of voting for that candidate, has been proven false numerous times. Most notably, Barack Obama's poll numbers were proven in two national elections to not be inflated. People polled will honestly say who they are voting for with no fear of social stigma.
The bottom line is I doubt the Shy Tory Theory, if it is even valid in the United Kingdom, is happening in the presidential election. Bad polling may be affecting matters. Trump and Clinton both over and under performed in various primary contests. Overall, the polls are a solid reflection of the state of the presidential campaign, as well as the most accurate way of predicting the eventual winner.