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.

Who's ahead in national polls?

DEMOCRAT

BIDEN

51%

REPUBLICAN

TRUMP

43%

Trend line showing average voting intention based on

individual polls

Show individual polls

average voting intention based on individual polls

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Date	BIDEN	TRUMP
30 Sep	51	43
30 Sep	51	43
30 Sep	51	43
29 Sep	51	43
29 Sep	51	43
29 Sep	51	43
28 Sep	50	43
27 Sep	50	43
27 Sep	50	43
26 Sep	50	43
25 Sep	50	43
25 Sep	50	43
24 Sep	50	42.5
24 Sep	50	42.5
24 Sep	50	42.5
23 Sep	50.5	42.5
23 Sep	50.5	42.5
22 Sep	50.5	42.5
22 Sep	50.5	42.5
22 Sep	50.5	42.5
22 Sep	50.5	42.5
21 Sep	51	43
21 Sep	51	43
21 Sep	51	43
20 Sep	51	43
20 Sep	51	43
19 Sep	50.5	43
19 Sep	50.5	43
19 Sep	50.5	43
18 Sep	50	43
17 Sep	50.5	43
16 Sep	50.5	43
16 Sep	50.5	43
16 Sep	50.5	43
15 Sep	50	43
15 Sep	50	43
15 Sep	50	43
15 Sep	50	43
14 Sep	51	43
14 Sep	51	43
13 Sep	51	43
12 Sep	51	43
12 Sep	51	43
11 Sep	51	43
10 Sep	51	43
10 Sep	51	43
09 Sep	51	43
08 Sep	51	43
08 Sep	51	43
08 Sep	51	43
08 Sep	51	43
08 Sep	51	43
08 Sep	51	43
07 Sep	49.5	42
06 Sep	49.5	42
06 Sep	49.5	42
05 Sep	50.5	42.5
04 Sep	50.5	42
04 Sep	50.5	42
03 Sep	50.5	42
02 Sep	50.5	42.5
02 Sep	50.5	42.5
01 Sep	50	42
01 Sep	50	42
01 Sep	50	42
01 Sep	50	42
01 Sep	50	42
01 Sep	50	42
31 Aug	50	42
31 Aug	50	42
31 Aug	50	42
31 Aug	50	42
31 Aug	50	42
30 Aug	50	41
30 Aug	50	41
29 Aug	50.5	41.5
28 Aug	50.5	42.5
28 Aug	50.5	42.5
27 Aug	50.5	42.5
26 Aug	50	43
25 Aug	50	42
25 Aug	50	42
25 Aug	50	42
24 Aug	50	42
23 Aug	50	42
22 Aug	50	42
21 Aug	50	42
20 Aug	50	42
19 Aug	50	42
18 Aug	50	42
18 Aug	50	42
18 Aug	50	42
17 Aug	50	42
16 Aug	50	42
15 Aug	50	42
15 Aug	50	42
14 Aug	50	41.5
14 Aug	50	41.5
13 Aug	50	41
12 Aug	50	41.5
12 Aug	50	41.5
11 Aug	50	41.5
11 Aug	50	41.5
11 Aug	50	41.5
11 Aug	50	41.5
10 Aug	49.5	41
09 Aug	49	41
08 Aug	49	41
07 Aug	49	41
06 Aug	49.5	41
05 Aug	49.5	41.5
04 Aug	50	42
04 Aug	50	42
03 Aug	50	42
02 Aug	49.5	41.5
01 Aug	49.5	41.5
31 Jul	49.5	41.5
30 Jul	49.5	41.5
29 Jul	49	41
28 Jul	49	41
28 Jul	49	41
28 Jul	49	41
27 Jul	50	41.5
26 Jul	51	41
25 Jul	51	41
24 Jul	51	41
23 Jul	51	41
22 Jul	50	41
21 Jul	50	41
21 Jul	50	41
20 Jul	50	40.5
19 Jul	51	41
18 Jul	51	41
17 Jul	50	40.5
16 Jul	50	40.5
15 Jul	50	40.5
15 Jul	50	40.5
14 Jul	50	40
14 Jul	50	40
13 Jul	50.5	40
12 Jul	50.5	40
12 Jul	50.5	40
11 Jul	49	40
10 Jul	49	40
09 Jul	49	40
08 Jul	49	40
07 Jul	49.5	40.5
07 Jul	49.5	40.5
06 Jul	49	41
05 Jul	49	40
04 Jul	49	40
03 Jul	49	40
02 Jul	49	40
01 Jul	49.5	40.5
30 Jun	49.5	40.5
30 Jun	49.5	40.5
30 Jun	49.5	40.5
29 Jun	50	41
28 Jun	49	41
27 Jun	49.5	40
26 Jun	49.5	40
25 Jun	50	41
24 Jun	50	41
23 Jun	49.5	40
23 Jun	49.5	40
22 Jun	50	41
22 Jun	50	41
21 Jun	50	41
20 Jun	50	41
19 Jun	50	41
18 Jun	50.5	41
17 Jun	50	41
16 Jun	50	41
16 Jun	50	41
15 Jun	49	41
14 Jun	49.5	41.5
13 Jun	49	41
12 Jun	49	41
11 Jun	49	41.5
10 Jun	49	42
09 Jun	49	42
08 Jun	49	42
07 Jun	49	42
06 Jun	49	42
05 Jun	49	42
04 Jun	48.5	42
03 Jun	49	42
03 Jun	49	42
03 Jun	49	42
02 Jun	48	41
02 Jun	48	41
01 Jun	48	42
01 Jun	48	42
31 May	48	41.5
30 May	48	42.5
29 May	48	42.5
28 May	48	42.5
27 May	48	42
26 May	48	42
25 May	48	42
24 May	48	42
23 May	48	42.5
22 May	48	42.5
21 May	48	42.5
20 May	48	42.5
19 May	48	43
19 May	48	43
18 May	49	44
17 May	49	44
16 May	48.5	43.5
15 May	48.5	43.5
14 May	49	43
14 May	49	43
13 May	48	43
12 May	47	43
11 May	47.5	42.5
10 May	47.5	42.5
09 May	47	42
08 May	47.5	42
07 May	47.5	42
06 May	47.5	42
05 May	48	42
04 May	48	42
03 May	47	42
02 May	47.5	41.5
01 May	48	42
30 Apr	47.5	41.5
29 Apr	48	42
28 Apr	48	42
28 Apr	48	42
27 Apr	48.5	42
26 Apr	48.5	42
25 Apr	48.5	42
24 Apr	48	42
23 Apr	48	42
22 Apr	48	42
21 Apr	48	42
20 Apr	48	43
19 Apr	48.5	42.5
18 Apr	48.5	42.5
17 Apr	48.5	42
16 Apr	48.5	42
15 Apr	48	42
14 Apr	48	42
13 Apr	48	42
12 Apr	47.5	42
11 Apr	47.5	42
10 Apr	47.5	42
09 Apr	47.5	42
08 Apr	48	42
07 Apr	48	42
07 Apr	48	42
07 Apr	48	42
06 Apr	49	42
06 Apr	49	42
06 Apr	49	42
05 Apr	48	42.5
04 Apr	48	43
03 Apr	48	43
02 Apr	48	43
01 Apr	48.5	44
31 Mar	49	45
30 Mar	49	45
29 Mar	49	45
28 Mar	49	45
27 Mar	49	45
26 Mar	49	45
25 Mar	49	44
24 Mar	49	43
24 Mar	49	43
23 Mar	50	44
22 Mar	50	44
21 Mar	52	42
20 Mar	52	43
19 Mar	52	43
18 Mar	52	42
17 Mar	52	42
16 Mar	52	43
15 Mar	52	43
14 Mar	52	43
13 Mar	52	43
12 Mar	52	43
11 Mar	51	43
10 Mar	50	43
09 Mar	51	42
08 Mar	51	42
07 Mar	50	43
06 Mar	49	45
05 Mar	49	45
04 Mar	49	45
03 Mar	49	45
02 Mar	49	45
01 Mar	49.5	45
29 Feb	50	45
28 Feb	50	44.5
27 Feb	50	44
26 Feb	49.5	44.5
25 Feb	50	45
24 Feb	50	45
23 Feb	50	45
22 Feb	50	44.5
21 Feb	50	44
20 Feb	50	44
19 Feb	50	44
18 Feb	50	44
17 Feb	51	44
17 Feb	51	44
16 Feb	50	43.5
15 Feb	50	43
14 Feb	50	43
13 Feb	50	43
12 Feb	49.5	45.5
11 Feb	50	44
10 Feb	49.5	43.5
09 Feb	49.5	43.5
08 Feb	49	44
07 Feb	49	44
06 Feb	49	44
05 Feb	50	46
04 Feb	50	45
03 Feb	50	45
02 Feb	50	45
01 Feb	50	44
31 Jan	50	44
30 Jan	50	44
29 Jan	50	44
28 Jan	50	44
27 Jan	50	45
26 Jan	50	45
25 Jan	50	45
24 Jan	50	46
23 Jan	50	46
23 Jan	50	46
22 Jan	50	44
21 Jan	50.5	45
20 Jan	50.5	45
19 Jan	50.5	45
18 Jan	48	46
17 Jan	48	46
16 Jan	48	46
15 Jan	48	46
14 Jan	48	46
13 Jan	48	46
12 Jan	48	46
11 Jan	48	46

62 days until Election day

The BBC poll of polls looks at the individual national polls from the last 14 days and creates trend lines using the median value, i.e. the value in the middle of the set of numbers.

See individual polls

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.

• A really simple guide to the US election

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.

• What is the electoral college?
• Predict the president: Play our game

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 about a 40% 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 Trump delivered on his promises?

Do polls show who won the first debate?

Donald Trump and Joe Biden went head-to-head in the first of three planned live TV debates on 29 September.

Many pundits called the debate for Mr Biden and the BBC's Anthony Zurcher agreed, describing it as "the political equivalent of a food fight" with the former vice-president emerging as the man "least covered in slop".

But what do the polls tell us? Well we'll have to wait a few days before the bigger national and state-level polls reflect any changes, but we do have some data from more limited snap polls.

In a CBS News/YouGov poll of people in battleground states who watched the debate, 48% said Mr Biden was the winner while 41% went for Mr Trump - a similar split to the national polling averages. Nearly 70% of people said the debate made them feel "annoyed".

A snap CNN poll gave Mr Biden a larger winning margin, with 60% of people saying he had won, compared to 28% for Mr Trump. But looking back to the first debate in 2016, a CNN poll then gave a similar winning margin to Hillary Clinton (62%-27%) and we know how that race ended.

• 'Chaotic, childish, gruelling' - Global media reaction
• Trump and Biden's debate claims fact-checked

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. But it dropped after that point, even among Republicans.

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 240,000 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.

• Trump deliberately played down virus, new book says

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.

• Americast: The latest news and gossip from the campaign trail

What questions do you have about the US election?

The US election process can be confusing. The BBC is here to help make sense of it. Please put your questions below.

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.