Your full guide to the US presidential election - crunch swing states and how to watch in the UK

Where are the crucial battlegrounds that could decide the election?

There are at least seven states that could be won by either Ms Harris or Mr Trump, and both campaigns have devoted significant time and energy to wooing voters in those places in recent weeks. Thanks to the Electoral College system, even if a race is close-run in one of these states, the victor can enjoy a huge boost, with 93 college votes up for the taking.

One cluster of states, known as the ‘blue wall’, spans Pennsylvania, Michigan and Wisconsin. All were Democratic strongholds for years, but after Mr Trump won across all three in 2016, the old certainties vanished as the Republicans sought to appeal to white voters without college degrees. Four years ago, President Joe Biden won all three of the midwestern battlegrounds, but some Democratic sources have suggested the party cannot be sure of winning Michigan and Wisconsin this time around. Significantly, the three states have all voted the same way going back to 1988.

Another group of so-called swing states consists of ‘Sun Belt’ states Arizona, Nevada, Georgia and North Carolina. No Democrat has won in the latter state since Barack Obama back in 2008, and Mr Biden was the first Democrat to secure victory in Georgia since Bill Clinton in 1992. Some polls have suggested that Democrats have lost support among black and Hispanic voters since 2020, which would potentially hinder their campaign in places like Georgia and Arizona.

A further ten states, including Florida, also represent some degree of uncertainty, with one candidate placing at around five to 10 per cent ahead of their opponent, according to the polls. The rest of the 33 states have an average margin of more than ten points, meaning they are highly unlikely to change their vote between either candidate. As an example, Ms Harris’s home state of California is sure to back her.

How tight is the race?

According to the latest data compiled by Five Thirty Eight showing national polling averages, Ms Harris has a slender lead at 48 per cent, with Mr Trump one percentage point behind. The polls have tightened considerably in recent weeks, and due to margins of error, the race for the White House is wide open.

In the battleground states, the outcome is even harder to predict. In Michigan and Wisconsin, Ms Harris has a lead of less than 1 per cent, with Mr Trump holding the same advantage in Pennsylvania and Nevada. The averages also suggest Mr Trump has a one point lead in North Carolina, a two point lead in Georgia, and as much as a three point lead in Arizona. But again, given the margin of error stands at around three to four percentage points, the outcome is anyone’s guess.

Is the polling data reliable?

The numbers coming in in recent days mean it is hard to say definitively who will win the race for the White House, but an important factor to bear in mind is the polls underestimated the support for Mr Trump when he won in 2016, and again in 2020, when he lost. The deficit is explained in part by Mr Trump’s voter base, who despite being staunch supporters of their man, tend to be less engaged.

Pollsters are increasingly using complex weighting methodologies to try and eliminate such underestimates in the 2024 election. Yet even the best informed pundits and political science experts would concede the models are far less precise than many people realise.

How could a candidate lose despite winning the most votes?

The Electoral College system, a convoluted system that has been in place since the 18th century, means US citizens do not directly choose the next president. Instead, each state has a certain number of electors allocated partly according to population, who then back the candidate voters favour.

There are 538 electoral college votes in total, and Ms Harris and Mr Trump need to gain a majority of the votes - 270 or more - to secure the keys to the Oval Office. Generally, states award all their electoral college votes to whoever wins the state-wide poll of ordinary voters. For example, if a candidate wins 50.1 per cent of the vote in Pennsylvania,, they are given all of the state's 19 electoral votes.

What if no one reaches the 270-vote threshold?

In this unlikely, though not impossible, scenario, a contingent election occurs, meaning the House of Representatives elects the next president, with each state casting one vote. A candidate needs a majority of 26 states to win.

This rare process last happened in 1824 when John Quincy Adams was elected by the House of Representatives after Andrew Jackson won the popular and electoral votes, yet fell short of a majority.

Where have the candidates focused their spending?

Unsurprisingly, the pivotal backgrounds detailed above are the focus of the vast sums being spent this electoral cycle. In Pennsylvania alone, the Democrats have spent more than $170 million [£131m] on advertising, with the Trump campaign not far behind on $137m [£106m], according to the latest data from AdImpact.

The Trump campaign is also spending big in Georgia, with an outlay of $83m [£64m]. The Harris election has spent $92m [£71m] on ads in that state, but it is also targeting voters across Michigan, where the spend stands at $129m [£100m].

What are the candidates’ final arguments?

Last week, Ms Harris made the symbolic decision to speak at the Ellipse in Washington DC, the very site where Mr Trump had told his supporters to “fight like hell”, shortly before they attacked the US Capitol in January 2021. In what was billed by her campaign as a “closing argument” speech,” she warned that her opponent was unstable, obsessed with revenge, consumed with grievance and “out for unchecked power”.

Mr Trump, meanwhile, has reverted to further cosplay-style performances. Having first donned a McDonald’s apron to serve fast food, he then dressed as a binman and drove a rubbish truck in Wisconsin, where he accused Mr Biden of calling his supporters “garbage”.

What are the key issues facing voters?

Several major policy points have dominated the campaign, and will continue to do so until the polls close. The economy has been central to the battle, and is an area where polling is split. Mr Trump has repeatedly blamed the Biden administration for inflationary pressures and the cost-of-living crisis. His plan to impose tariffs on foreign goods, part of a populist economic agenda, may appeal to his base, but economists have warned it could lead to further price spikes. Ms Harris has garnered support after promising higher corporate tax rates, and a ban on food price gouging.

As was the case in 2016 and again four years ago, the Trump campaign is also focusing on immigration, and has promised to deport millions of people. Ms Harris, for her part, has spoken extensively about abortion, and has made reproductive rights a key flank of her appeal to voters.

How can I watch the election unfold?

Aficionados of US politics this side of the Atlantic are spoiled for choice when it comes to watching the results unfold. Early birds will be able to tune in to Sky News from 10pm on Tuesday evening for 12 hours of continuous election night coverage, hosted by Mark Austin and Yaldi Hakim in Washington DC.

In a sign of how important the vote is, Channel 4 will also broadcast its first overnight US election show since 1992. It will kick off its coverage from 10.15pm, and has promised an eclectic range of guests, including Boris Johnson, Brian Cox and Stormy Daniels.

The BBC’s US election results programme will begin at 10.40pm on BBC One and the BBC News Channel, and run throughout the night until breakfast time, bringing key results and analysis. Tom Bradby, meanwhile, will helm ITV’s programme, ‘Harris V Trump: The Results’ live from Washington DC from 10.45pm. For those who prefer podcasts for their political coverage, Rory Stewart and Alastair Campbell from The Rest Is Politics will be hosting a livestream on YouTube.

Are there election watch parties taking place in Scotland?

Other than a “post-election party” scheduled for Wednesday in London, the Republicans Overseas group has not announced any election events on its site. But Democrats Abroad, the official arm of the Democratic Party overseas, is hosting a watch party at The Three Sisters in Edinburgh’s Cowgate.

It has a special reserved area booked for between 11pm and until 5am. A message promoting the event on the group’s Facebook page offers a hint of what lies ahead. “Come celebrate the election of the first female president, or alternatively, the beginning of the end,” it states.

What will be the early signs of how Americans have voted?

The first details of exit polls that were conducted will be revealed after 9pm, but they will only be announced in states with large margins between the candidates. The polls in numerous swing states will close between between 11pm and 2am, and there could be early indications of who the electorate has chosen shortly afterwards. 

In some cases, states have laws allowing ballots postmarked by election day to be counted even if they arrive later. This process can lead to delays in certain states, particularly those with narrow margins. It is worth recalling that in 2020, no less than seven key states, including Georgia, North Carolina, and Pennsylvania, remained uncalled the morning after the election. 

When will the final results be known?

As was the case four years ago, it could be several days before we have a definitive set of results. Back then, the election was also held on a Tuesday, but Mr Biden was not officially declared as the winner until the Saturday afternoon. 

Thanks to the close run race, the number of mail-in ballots (voters in the likes of Oregon and Utah have their say almost entirely by mail), different states’ rules on processing votes, and the fact that, irrespective of the results, Mr Trump is highly unlikely to concede, there is every chance we could be waiting a while.

Rules on how and when a recount is triggered or can be requested vary from state to state, but there is, at least, a cut-off point. This year, under a new law, states have until December 11 to ascertain a winner to guarantee their electoral votes are counted.

Should I expect to hear election-related conspiracy theories?

If the experience of 2016 and 2020 is any guide, then absolutely. Mr Trump has already repeatedly claimed that non US citizens have been voting in significant numbers, an allegation for which there is not a shred of evidence. It is one of a number of conspiracy theories that have circulated online in the lead up to the election, and that trend will likely intensify as the business end of the election comes into sight.

Amid a torrent of familiar and unproven allegations around fake ballots and fraudulent mail voting, officials who will oversee the vast count have already taken steps to deal with the fallout. In Wisconsin, for example, election workers have been trained on de-escalation techniques, and polling stations have been rearranged so as to allow workers to seek a safe place if they are confronted by protestors.