This year North Carolina, Florida, Michigan, Wisconsin, and Arizona could all be decisive in the election’s outcome. They are all states which Mr Trump won narrowly against Mrs Clinton in 2016, helping him secure his electoral college victory. Retaining them is crucial to his re-election hopes.
If the polls are to be trusted, Mr Biden holds a competitive edge over Mr Trump in all of them. Pollsters attributed Mr Biden’s lead to support among white university-educated voters, while Mr Trump’s support among white working-class voters is waning.
Read more: US Election 2020 polls tracker
What happens on Election Day?
On November 3, voters who have not sent a mail-in ballot will head to the polls. The colossal task of counting votes begins later that day.
Millions of Americans will vote on Election Day.
Some news networks and pollsters will publish projected results late on Nov 3, though these results are provisional while mail-in ballots are counted.
Election results timetable
Mail-in ballots can be received late and will still be counted in many states.
Most mail-in ballots must be received within a couple of days of November 3, with a few exceptions. Some key states allow ballots to be sent in late, including Pennsylvania and North Carolina (by Nov 6), Minnesota and Nevada (by Nov 10), and Ohio (by Nov 13).
Each state begins to certify its results from November 10, though this too can be delayed if there is a recount. Every state except California must complete the certification by Dec 8. All disputes – including challenges and recounts – must be resolved by this date.
Electors formally cast their votes on December 14 and send them to Washington.
This means that the clear result of the election – which has been drastically impacted by postal ballots because of coronavirus – might not be known until some time after Election Day.
How many electoral votes are needed to win?
To win the presidency, Mr Trump or Mr Biden must get more than 50 per cent of the Electoral College vote. There are 538 possible electoral votes, which means 270 are required to win.
What time do voting polls open and close?
The opening and closing times for polling stations vary from state to state, in some cases by city or county.
Some states allow people waiting in the queue when the polling station closes to cast their vote – some do not.
Most polls open at 6am and the latest they stay open is until 9pm (in New York and North Dakota).
In Vermont, early-risers can cast their vote at 5am.
All polling stations will close by 9pm ET on Nov 3 (2am UK time on Nov 4).