By The Visual and Data Journalism Team BBC News – BBC.COM
Voters in America will decide on 3 November whether Donald Trump remains in the White House for another four years.
The Republican president is being challenged by Democratic Party nominee Joe Biden, who is best known as Barack Obama’s vice-president but has been in US politics since the 1970s.
As election day approaches, polling companies will be trying to gauge the mood of the nation by asking voters which candidate they prefer.
We’ll be keeping track of those polls here and trying to work out what they can and can’t tell us about who will win the election.
Biden leading national presidential polls
National polls are a good guide as to how popular a candidate is across the country as a whole, but they’re not necessarily a good way to predict the result of the election.
In 2016, for example, Hillary Clinton led in the polls and won nearly three million more votes than Donald Trump, but she still lost – that’s because the US uses an electoral college system, so winning the most votes doesn’t always win you the election.
With that caveat aside, Joe Biden has been ahead of Donald Trump in most national polls since the start of the year. He has hovered around 50% in recent months and has had a 10-point lead on occasions.
By contrast, in 2016 the polls were far less clear and just a couple of percentage points separated Mr Trump and his then-rival Hillary Clinton at several points as election day neared.
Which states will decide this election?
As Mrs Clinton discovered in 2016, the number of votes you win is less important than where you win them.
Most states nearly always vote the same way, meaning that in reality there are just a handful of states where both candidates stand a chance of winning. These are the places where the election will be won and lost and are known as battleground states.
In the electoral college system the US uses to elect its president, each state is given a number of votes based on how many members it sends to Congress – House and Senate. A total of 538 electoral college votes are up for grabs, so a candidate needs to hit 270 to win.
As the map above shows, some battleground states have a lot more electoral college votes on offer than others so candidates often spend a lot more time campaigning in them.
Who’s leading in the battleground states?
At the moment, polls in the battleground states look good for Joe Biden, but there’s a long way to go and things can change very quickly, especially when Donald Trump’s involved.
The polls suggest Mr Biden is ahead in Michigan, Pennsylvania and Wisconsin – three industrial states his Republican rival won by margins of less than 1% to clinch victory in 2016.
But it’s the battleground states where Mr Trump won big in 2016 that his campaign team will be most worried about. His winning margin in Iowa, Ohio and Texas was between 8-10% back then but it’s looking much closer in all three at the moment.
Betting markets, however, are certainly not writing Mr Trump off just yet. The latest odds give him just less than a 50% chance of winning on 3 November, which suggests some people expect the outlook to change a lot over the next few weeks.
But political analysts are less convinced about his chances of re-election. FiveThirtyEight, a political analysis website, says Mr Biden is “favoured” to win the election, while The Economist says he is “very likely” to beat Mr Trump.
Has coronavirus affected Trump’s numbers?
The coronavirus pandemic has dominated headlines in the US since the start of the year and the response to President Trump’s actions has been split predictably along party lines.
Support for his approach peaked in mid-March after he declared a national emergency and made $50 billion available to states to stop the spread of the virus. At this point, 55% of Americans approved of his actions, according to data from Ipsos, a leading polling company.
But any support he had from Democrats disappeared after that, while Republicans continued to back their president.
By July, the data suggests his own supporters had begun to question his response – but there was a slight uptick in August and September.
The virus is likely to be at the forefront of voters’ minds and one leading model produced by experts at the University of Washington predicts the death toll will have risen to about 230,000 people by election day.
Mr Trump may be hoping Operation Warp Speed, his administration’s vaccine initiative, can produce an “October surprise” – a last-minute event that turns the election upside down.
The chief scientific adviser to the initiative has said it’s “extremely unlikely but not impossible” that a vaccine could be ready to distribute before 3 November.
Can we trust the polls?
It’s easy to dismiss the polls by saying they got it wrong in 2016 and President Trump frequently does exactly that. But it’s not entirely true.
Most national polls did have Hillary Clinton ahead by a few percentage points, but that doesn’t mean they were wrong, since she won three million more votes than her rival.
Pollsters did have some problems in 2016 – notably a failure to properly represent voters without a college degree – meaning Mr Trump’s advantage in some key battleground states wasn’t spotted until late in the race, if at all. Most polling companies have corrected this now.
But this year there’s even more uncertainty than normal due to the coronavirus pandemic and the effect it’s having on both the economy and how people will vote in November, so all polls should be read with some scepticism, especially this far out from election day.
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Written and produced by Mike Hills and Will Dahlgreen. Design by Irene de la Torre Arenas. Development by Katie Hassell, Marcos Gurgel, Steven Connor and Shilpa Saraf.