Pace yourself. The presidential election is almost upon us, but it could take days – even weeks – to get a clear result after polling day on 5 November. Maybe if it’s either a Republican or Democrat landslide, we’ll get an immediate result, but that would mean the opinion polls have been hopelessly wrong.

The mechanics of a US election night are entirely different to anything we are used to in Britain or many other democracies for that matter. In the US, the name of the game is to get to 270 electoral college votes. And if that sounds confusing, imagine it as a board game with five rows of 10 squares, where each square represents one of the 50 states.

Each state, depending on its population size, is allocated a number of electoral college votes on a winner-takes-all basis (there is a Nebraska and Maine exception, but that’s a whole different story). California is the biggest, with 54 electoral college votes; South Dakota, Vermont and Wyoming are the smallest with 3 votes apiece.

The total number of votes available is 538. So, once you hit half that number plus one – 270 – you’re home and dry and measuring up the curtains on the Oval Office.

The results will be announced on TV – it is the TV networks or wire services like the Associated Press that “call” a state – in other words, make the judgement whether it is a Democrat or Republican victory.

AP says it does not make predictions or speculate about likely winners. It has a “decision team” made up of researchers, analysts and race callers. It collects voting data from county clerks, local officials and other electronic data feeds from across the 50 states.

Those results, says AP, are then “combined with research including demographic data, voting history and statistics about advance voting – to declare winners”.

Controversially, last time round Fox News enraged Donald Trump by calling Arizona as a Dem gain, way before any other network – undermining the Trump plan to declare victory come what may. They called it well before all the votes had actually been counted, but they got it right. Arizona had been carried by Biden.

It doesn’t always go quite so smoothly. In 2000, the major TV networks along with AP called Florida for Al Gore, before beating a hasty retreat amid controversy over voting machines and “hanging chads” (remember them?). It took more than a month for the Supreme Court to ultimately decide the state had been won by George W Bush.

Because the US straddles multiple time zones, the polls close in different states at different times. On the east coast, it will be three hours earlier than the west. So there is no grand moment when the networks announce the result of a nationwide exit poll.

But with a large number of states, the results are almost instantaneous. I am sure, for example, we won’t have to wait long on election night for Kentucky or Tennessee, say, to be called for Trump – or for Connecticut or Rhode Island to be called for Harris.

It is the seven swing states that are going to keep us awake all night – and possibly and probably the following day and night too. In 2020, polling was (as it always is) on Tuesday – but we didn’t get the result in Pennsylvania – the key state that would push Biden over the line – until mid-morning on Saturday.

CNN was the first to call the presidency for Biden on that day. It was followed within two minutes by NBC, MSNBC, CBS and ABC – and they were followed soon after by AP and Fox.

Then there is the method of voting. In the UK we are used to being handed a ballot paper with the names and party of the candidates standing for that constituency. If there is a local council election taking place on the same day, we will get another ballot paper for that contest.

In the US you will have at the top of the “ticket” the fight for the president, then the Senate, and the House. And the ballot paper will go on and on – election for the governor of the state, state senate, councilmen and women, school boards, town councils – even down to the dog catcher. You can end up with a ballot paper the best part of a metre long because you are being asked to vote for so much.

Each state has its own rules on how the election will be managed and their own voting machines. In some states, there will be myriad different machines within the state. (Voting machines were not only a big story back in Florida in 2000 – Fox News was forced to pay out almost $800m to Dominion Voting Systems after the 2020 election for falsely claiming that the company’s machines were switching votes for Trump to Biden.)

This time around under the state’s election law, the counting of postal votes in Pennsylvania won’t begin until 7am on election day. The same law applies in Wisconsin. Yet other states are counting as the mail-in ballots come in, meaning we should get results more quickly. Yet in those two key swing states, it is likely going to delay the result.

And it is up to individual states to decide how to offer mail-in ballots, whether in-person early voting is permitted. In Georgia – another swing state – the great tradition was that in the Black churches on the last Sundays before polling, buses would take the faithful to vote early at polling stations nearby. Long queues would form and volunteers would hand out bottles of water.

The African American vote in the US is traditionally massively pro-Democrat. So Republicans in control of the state passed local laws banning volunteers from handing out food or water to people waiting in line. The rationale was that it constituted election interference. Others saw a much more sinister motive behind it.

That takes us to the final distinction. There will be literally thousands of lawyers on call for both the Democrats and the Republicans in all 50 states ready to litigate anything and everything in the conduct of this election.

If the looming presence of lawyers is the biggest difference between covering elections in the US and UK, there are others.

On the night of the UK general election in 1997, the British ambassador in Washington hosted a watch party at the magnificent Lutyens residence for the good and the great of DC. Among the invitees was a longstanding Democrat congressman from Massachusetts. He had fought and won his district about a dozen times and was transfixed by the coverage on the BBC of the UK election night.

Why? He was mesmerised by the sight of all the different returning officers in sports halls up and down the country, pulling the candidates together on stage, and announcing the results, while the victor shook hands with those he or she had vanquished. This rather grand congressman turned to a diplomat friend of mine and said: “You know I have never once met any of my political opponents.”

That isn’t the case for Trump and Harris – but however the result goes, don’t expect a public concession sealed with a handshake in a school gymnasium or leisure centre.