Republican Donald Trump and Democrat Hillary Clinton during the first presidential debate at Hofstra University on Sept. 26. Photo: Screenshot.

It’s the most important, and unasked, question of the 2016 election cycle: How reliable are the polls?

In England’s 2015 prime ministerial elections, all 92 polls were wrong. Most polls showed Labour leader Ed Miliband ahead of David Cameron, while a few showed a tie. On election morning, Miliband predicted victory, but by nightfall voters had balloted him into oblivion. The polls were all wrong. Not only did they miscalculate the overwhelming vote for Cameron, but they also underestimated the Conservative Party’s gigantic win in parliament.

The Brexit polls were no less dramatic in their wide margin of error. Most polls showed that UK voters were inclined to stay in the EU. Instead, voters chose to leave the EU — and by a comfortable margin.

What had an impact on the Brexit vote? Concerns about immigration and border security.

And why were the polls flawed? Because many voters were too shy to express their true preferences.

Immigration and security are major factors in this election, and those who don’t want to be viewed by some as “racist” — or might be embarrassed about voting for Trump — might conceal their true preferences.

How many shy voters are missing from our polls? How many dissatisfied workers furtively plan to switch loyalties on election day? How many of these polls can we trust?

Other countries are aghast as we painfully elect their next world leader. Many Americans may relinquish the current unsavory task altogether and stand aside. The polls cannot predict how many people will sit out this election.

We won’t know until Election Day how accurately our polls will represent our electoral vote, but one thing is certain: on election night, half the country will breathe a sigh of relief, while the other half will go into acute, excruciating mourning.

See you at the polls.