The 2020 presidential race is taking place in significantly different circumstances than four years ago because of the Covid-19 pandemic, with millions voting early or by post.
Americans were watching anxiously on Wednesday as results poured in from around the US but election officials warn that it could take days, or even weeks, before it is clear whether Donald Trump or Joe Biden is the victor.
When will we know who the next president is?
The next occupant of the White House, whether that be Republican Mr Trump or Democrat Mr Biden, will be decided by the Electoral College. A candidate must win 270 Electoral College votes to claim the presidency.
Each state is allotted a different number of electoral college votes, based roughly on the size of its population.
Why have we not had a result yet despite polls closing hours ago?
There is added caution in calling the winner of each state this year due to the diverse ways that US voters cast their ballots in 2020 because of the Covid-19 pandemic.
More people than ever cast their vote ahead of election day with mail-in ballots. While Wisconsin and Michigan were eventually called for Mr Biden on Wednesday afternoon, results may not come in from the key battleground of Pennsylvania until Thursday, potentially Friday.
Final results were also pending in Alaska, Arizona, Georgia, North Carolina and Nevada.
What if the election is a tie?
If there is a tie – 269 electoral college votes a piece – then the newly-elected House of Representatives would choose the next president, with each state delegation having one vote.
A simple majority of states, equivalent to 26 votes or more, would be needed to win.
If the election result is disputed, Mr Trump has repeatedly suggested that the decision could end up in the Supreme Court, a claim he reiterated in the wee hours of Wednesday.
At a White House press conference he said: “We’ll be going to the US Supreme Court.
“We want all voting to stop. We don’t want them to find any ballots at four o’clock in the morning and add them to the list.”
Is there an absolute deadline?
Inauguration Day – always 20 January – or 21 January if the 20th falls on a Sunday. The date is set in the US Constitution, under the 20th Amendment enacted in 1933, so a president must be decided by then.