The world's fate in their hands The seven key battleground states that will decide the presidency

Spare a thought for beleaguered Pennsylvanians. Over the past few weeks they have been pummelled with $280m-worth of campaign ads, part of an eye-popping $2.1bn spent so far on the US presidential election.

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Pennsylvania is one of the seven battleground states that, when it comes to choosing presidents, can seem as revered as the seven wonders of the world. These states, come 5 November, will decide the outcome of one of the most consequential elections in modern times.

Their names are seared into the minds of politically aware Americans: Arizona, Georgia, Michigan, Nevada, North Carolina, Pennsylvania and Wisconsin. Under the country's arcane system, the occupant of the White House is elected not through the popular vote but by electoral college votes harvested state by state.

Between them, the seven states control 93 electoral votes. In the final days, Donald Trump and Kamala Harris, and their running mates JD Vance and Tim Walz will be scrambling all over them in an effort to reach the 270 electoral votes required to win.

These states are called battlegrounds for a reason - their loyalty cannot be taken for granted by either side. This year, though, their unpredictability has reached dizzying heights. The Guardian's presidential poll tracker shows five of them essentially tied within a three-point margin of error, with only Arizona (where Trump is up by four points) and Wisconsin (where Harris is up by five) pulling away.

Nate Cohn, the New York Times's chief political analyst, has drily noted that the presidential polls are "starting to run out of room to get any closer". Ed Pilkington

Arizona

'Why isn't Trump doing a little better here?'

On a stiflingly hot afternoon last month, Lynn and Roger Seeley relaxed into an air-conditioned co-working space in a suburb east of Phoenix. They had come to hear the Democratic candidate for the US Senate, Ruben Gallego, make his pitch to a roomful of small-business owners. Lifelong Republicans, they might have felt out of place at a Democratic campaign event in the pre-Trump era. But not now.