But it has conducted a “poll” of voters in every election since 1980 to express a preference, and will still send its result to Congress. In most cases (Trump’s 2016 victory being an exception) the outcome in Guam aligned with the eventual national winner. As the territory is 15 hours ahead of the US mainland, its poll will be looked at as an early indicator of the final result.

The results are then declared for each county within the states as they are counted in the hours following the close of polls. Key precincts and counties to watch for include Door County in Wisconsin and Northampton County in Pennsylvania, both of which have a history of supporting the eventual winner.

The TV networks and the Associated Press play an important role and compete to declare their winners, “calling” the states that they voted for one candidate or another when they believe they have enough results from the polling stations. Then, when they are confident, the media networks will finally call the overall winner as well. With huge reputational risk involved if they’re wrong — and if the contest is as close as the polls predict — it could be a while before anyone is brave enough to call him.

What are the issues that define the campaign?

Harris has made supporting abortion rights the centerpiece of her campaign. Since the Supreme Court overturned Roe v. Wade in 2022, states introduced their own measures to restore women’s voting rights, a policy that is popular nationally. She attacked Trump’s character, describing him as a fascist and arguing that the future of democracy is on the line.

For his part, Trump emphasized the economy, promising tax cuts and criticizing Biden’s record overseeing a period of high inflation. A crackdown on immigration remains an explosive and central part of his policy offering, and he frequently court controversy to convey his point of view.

Could the polls be wrong?

Of course. The poll is a media obsession and generates enormous amounts of coverage, dominating the contest and shaping the entire debate. But the polls’ record in the recent US presidential election is poor.