On the night of the US presidential election, November 3, polls will close at different times across the United States, usually on the hour.
As soon as this happens, a state can be "called" by the US news networks for either Donald Trump or Joe Biden.
This will take place only when the networks are confident that a candidate will win the state.
For those states that traditionally vote solidly Republican (such as Wyoming and Oklahoma) or Democrat (California and New York), it is likely to happen almost the moment the polls close, before a single vote has been counted.
But where the race is expected to be close, in swing states such as Florida, Michigan or Pennsylvania, the networks will want to wait until a significant number of votes are actually counted and reported before making a projection. And because of this, some states might not be called for hours, and possibly days.
Here is a guide to how US election night is likely to unfold. In all cases, the time given is when the last polls close in each state. All times are GMT.
-November 4 Donald Trump should be off the mark when polls close in three traditional Republican strongholds: Indiana, Kentucky and South Carolina.
Joe Biden will pick up the safe Democratic states of Virginia and Vermont. Polls also close in one swing state: Georgia. But if the result here is close, as is likely, don't expect the state to be called immediately.
-West Virginia, a safe Republican state, should be called for Mr Trump. Two swing states that the President won in 2016, North Carolina and Ohio, also close their polls at this point.
The majority of votes in both states are expected to be reported quickly, but if no winner is clear on the night then the final outcome might not be known for days, once all the absentee ballots are counted.
-A rush of projections are likely when polls close in more than a dozen safe states.
Mr Biden should pick up the solid Democratic states of Connecticut, Delaware, Illinois, Maine, Massachusetts, Maryland, New Hampshire, New Jersey, Rhode Island and Washington DC.
Mr Trump ought to see Alabama, Mississippi, Missouri, Oklahoma and Tennessee added to his tally.
Polls are also due to close in two absolutely crucial swing states, Florida and Pennsylvania. Pennsylvania was solidly Democrat until Mr Trump won it narrowly in 2016, but it has been heavily targeted by Mr Biden.
However due to the huge number of postal and early votes cast this year, which will need to be sorted and counted, the outcome might not be clear for some time.
By contrast, Florida - always a nailbiter - is expected to count its votes quickly and as such should give a fairly swift indication of how both the candidates are faring.
-Polls close in Arkansas, another strongly Republican state.
-Both candidates ought to collect a decent number of votes when polls close in a handful of strongholds.
Kansas, Louisiana, Nebraska, North Dakota, South Dakota and Wyoming should all be called for Mr Trump.
Mr Biden ought to collect Colorado, Minnesota, New Mexico and New York.
Texas will be one to watch - traditionally Republican, it is edging closer to becoming a swing state, though probably won't change hands this year.
Three swing states are also up for grabs, all of which were won by the President in 2016: Arizona, Michigan and Wisconsin.
Polls suggest Mr Biden could gain Wisconsin and Michigan, while Arizona is too close to call.
-Mr Trump will add two more states to his tally when polls close in the safe Republican states of Montana and Utah.
Nevada should be called for Mr Biden.
Polls also close in the last of the swing states, Iowa, which Barack Obama won in 2008 and 2012, Mr Trump won in 2016, and where Mr Biden could have an outside chance of a gain.
-Mr Biden's numbers will get a boost when polls close in three very safe Democratic states: California, Oregon and Washington. Idaho should be called for Mr Trump.
-Polls close in another safe Democratic state, Hawaii.
-Alaska is the last state to conclude voting, and should be called for Mr Trump. But there is every likelihood that the overall winner of the election still won't be known, given the time it will take to count all the ballots in all the swing states.
If there has been a landslide for either Mr Trump or Mr Biden, then some news networks might be tempted to name a winner by now.
If it shaping up to be a close contest, get ready to wait days, if not weeks, for the identity of the next president to be confirmed.
Here are five scenarios for what could happen this year.
The polls are wrong again. Joe Biden fails to get enough support in states that Donald Trump won narrowly in 2016 - places like Pennsylvania and Michigan - while losing badly in longshots like North Carolina and Georgia. Were no states to change hands, the result would be a repeat of four years ago, with Joe Biden winning 232 electoral votes and Donald Trump 306.
(A total of 270 electoral votes are needed to win the US presidential election. Each state is allotted a fixed number of electoral votes, based roughly on the size of its population. Whoever wins the popular vote in a state also wins all of that state's electoral votes - with two exceptions being Maine and Nebraska, which divide up their electoral votes partly based on who wins the popular vote.)
In this scenario Joe Biden gains a couple of extra states, but doesn't pick up quite enough electoral votes to make it to 270. For example, winning Michigan (worth 16 electoral votes) and Wisconsin (10) would increase Biden's tally from 232 to 258: 12 short of the winning line. Donald Trump's tally would fall from 306 to 280, but he'd still be safely above the 270 mark. Trump can therefore afford to lose one or two states to his opponent, but no more than that.
Gaining just three states - the former 'blue wall' of Michigan (16 votes), Pennsylvania (20) and Wisconsin (10) - would be enough to put Joe Biden above 270, taking his tally from 232 to 278. Alternatively Biden need only pick up Florida (29 votes) and Arizona (11) to also be over the 270 mark. Or he could go for a mix of northern and southern states, for example Pennsylvania and Florida. Biden has a number of paths to reach the magic number of 270, though a narrow victory could be more likely to invite legal challenges - justified or otherwise - from Trump.
If the polls turn out to be not just snapshots but accurate predictions, and are even understating Joe Biden's popularity, then Biden could be heading for seven or even eight gains from Donald Trump. An example of a landslide win would be if Biden picks up Arizona (11 votes), Florida (29), Michigan (16), North Carolina (15), Ohio (18), Pennsylvania (20) and Wisconsin (10): a total of 119 additional electoral votes, leaving him with a grand total of 351 compared with Trump's 187. By way of a comparison, in 2008 Barack Obama won 365 votes to John McCain's 173.
This is possible. Were Joe Biden to pick up Michigan (16 votes), Pennsylvania (20) and one of Maine's four electoral votes, both he and Donald Trump would be tied on 269 electoral votes. Similarly, if Biden gained Michigan (16) plus Wisconsin (10) plus Arizona (11), both he and Trump would end up with 269 each. In this situation, the newly-elected House of Representatives would choose the president, with each state delegation having one vote. A majority of states (26) would be needed to win.