But it has conducted a “straw poll” of voters in every election since 1980 to express its preference and will still send its results to Congress. In most cases (with the exception of Trump's victory in 2016), Guam's result was consistent with the eventual national winner. Because the area is 15 hours ahead of the U.S. mainland, the straw survey is being examined as a leading indicator of the final result.

Results are then announced for each county within the state as they are counted in the hours after voting ends. Key counties and counties to watch include Door County in Wisconsin and Northampton County in Pennsylvania, both of which have been shown to support the eventual winner.

Television networks and the Associated Press play an important role, vying to announce winners by “calling” states as having voted for one candidate or another when they believe they have enough results in the electoral districts. If they are confident, the media networks will eventually name the overall winner. If they get it wrong, there's huge reputational risk – and if the contest is as close as the polls predict – it could be a while before anyone has the courage to call it out.

What themes shape the campaign?

Harris has made advocating for abortion rights the core of her campaign. Since the Supreme Court overturned Roe v. Wade in 2022, states have proposed their own measures to restore women's right to vote, a policy that has been popular across the country. She has attacked Trump's character, calling him a fascist and arguing that the future of democracy is at stake.

Trump, for his part, has placed emphasis on the economy, promising tax cuts and sharply criticizing Biden's record in overseeing a period of high inflation. Tackling immigration remains an explosive and central part of his policy offering, and he often courts controversy to push his point.

Could the polls be wrong?

Naturally. Polls are a media obsession, generating huge coverage, dominating the competition and shaping the entire debate. But the pollsters' assessment of the recent US presidential elections is poor.