US election 2020: What to look out for on election night

On 3 November, Americans will head to the polls and send either Joe Biden or Donald Trump to the White House.

Here's what to watch for as an unpredictable election night unfolds, and the results roll in.

The influx of postal ballots this year will make it hard to see who's in the lead early on.

Different states have different rules for how - and when - to count postal ballots, meaning there will be large gaps between them in terms of reporting results. Some states, like Florida and Arizona, begin pre-processing ballots weeks before 3 November. Others, like Wisconsin and Pennsylvania, won't touch these votes until election day, meaning they'll likely be slower to count.

To add to the confusion, states differ in their deadlines for when to accept postal ballots. Some, like Georgia, will only count ballots received on or before 3 November, while others, like Ohio, will count late ballots as long as they are postmarked by 3 November.

We know for certain that in some states it will take weeks to get complete results, meaning it will be nearly impossible to predict when we can officially name the next president.

This hasn't been the case in past elections, when you could typically set your watch to the 23:00 EST (04:00 GMT) closure of West Coast polls. In 2008, results came right on the hour and in 2012 they were just 15 minutes after that.

The last time around, however, it wasn't until Donald Trump clinched Pennsylvania deep into election night - 01:35 EST (06:35 GMT) - that his victory over Hillary Clinton was considered inevitable.

There will be a few extra things to keep an eye on this year.

For one, early tallies may be deceptive. This is due in part to more differences between states in reporting.

In some states, ballots cast in person on election day will be tallied first. These are expected to favour Mr Trump, as early polls show his supporters plan to cast ballots on 3 November.

But in others, postal votes cast prior to 3 November will be reported first or included in early counts along with day-of votes. Initial results from these states may favour Mr Biden, as Democrats are more likely than Republicans to vote by mail this year.

There's also the looming concern of electoral fraud - a common refrain from the Trump campaign. Importantly, instances of electoral fraud are incredibly rare, and there is no evidence that postal ballots are especially susceptible. Overall, the rate of voting fraud in the US is between 0.00004% and 0.0009%, according to a 2017 study by the Brennan Center for Justice.

If there are no clear results on 3 November we'll have to wait days - or weeks - for vote counting to finish up.

It's normal that all the votes aren't tallied up on the night but this year it may take even longer.

Plus, there could be legal disputes which will add to the uncertainty and could mean the courts play a part.

We know that final results will be slow, but there are still some states that may give us early clues.

Polls will close in North Carolina at 19:30 EST (00:30 GMT), where a large number of early in-person voters means projections could come quickly. Donald Trump narrowly won this state in 2016 and it is a toss-up between parties once again. A win here for Mr Trump or Mr Biden could mean a good night ahead.

Soon after, at 20:00 EST (01:00 GMT) the last polls will close in Florida. Elections have been won and lost in this battleground state, and the same may be true this year. A note of caution: early in-person and postal ballots will be reported first in Florida and these will likely favour Mr Biden.

And at 21:00 EST (02:00 GMT), polls will shutter in Arizona, where officials began counting ballots on 20 October. Trump was victorious here in 2016, but national polls now give Mr Biden a razor's-edge lead. In Arizona, like Florida, early counts may favour Mr Biden, whose supporters are more inclined to vote early or by mail.

In a number of other states, officials will not count a single ballot until 3 November. This means we'll have to wait for a number of swing states, whose results are crucial for a clear picture of the country.

In Ohio, polls will close at 19:30 EST (00:30 GMT). Officials will provide preliminary results on election day but then no further counts will be released until the final totals are certified, which must be done by 28 November. Ohio is not just a swing state, it is also a presidential fortune-teller: it has backed the winner at every presidential contest since World War Two.

Polls in Pennsylvania will shutter at 20:00 EST (01:00 GMT) on election day. Both candidates' likely path to the White House will run through this battleground state, the place where Mr Biden was born and which Mr Trump won in 2016 by a single percentage point.

In both Wisconsin and Michigan, polls will close at 21:00 EST (02:00 GMT). Democrats have been hard at work in Wisconsin after Hillary Clinton's narrow loss there in 2016 . Some polls now give Mr Biden the lead, but the state is still up for grabs. Neighbouring Michigan - another swing state - will also be closely watched, and is seen as critical to victory for both Biden and Trump.

Biden and Trump aren't the only two people on the ballot.

Both parties will be paying close attention to elections for the US Senate - where Republicans currently hold a three-seat advantage.

Trump ally Lindsay Graham is in the fight of his political life in South Carolina, facing a stiff challenge from Democrat Jaime Harrison. Mr Graham has held this seat since 2003, but he has turned away some voters with his staunch loyalty to the president.

In Maine, Republican Susan Collins may soon be out of a job. Ms Collins is one of the few moderate members of her party in office right now, but she still may be punished for her affiliation to the president in a state where he is deeply unpopular.

And that's not all. Americans will also weigh in on more than 100 ballot measures. In California, a referendum is looking to overturn a law which eliminates cash bail entirely, and replaces it with a pre-trial risk assessment.

Marijuana is on the ballot in Arizona, Montana, New Jersey and South Dakota, where voters could legalise cannabis for recreation purposes. Similarly, in Mississippi, voters may cast their ballots to approve marijuana for medical purposes.