Watch: How Britain’s voting system works

Constituencies vary in size geographically, but typically each will have between 60,000 and 80,000 voters.

All British citizens resident in the country and aged 18 years old or over on December 12 will be able to cast their ballot, with some 46 million people reportedly registered to vote.

Voters choose one person from a list of candidates to represent their local area — and the candidate that receives the most votes wins.

All of the elected MPs then enter parliament to sit in the House of Commons and represent the people in their constituency.

The political party that secures the most MPs is invited by the Queen to form the government.

An absolute majority in parliament is 326 seats, although the number for a working majority is slightly lower in practice. That’s because lawmakers elected for Sinn Fein in Northern Ireland actively abstain from taking up their seats in Westminster — since the party rejects Britain’s claim to sovereignty over Ireland.

So for example, in the 2017 election, seven Sinn Fein MPs were elected. This effectively lowered the threshold for a majority to 322.

If there is a clear result after polls close at 10 pm on election day, we can expect to see opposition leaders announcing that they have conceded to the winner.

But, if recent history is to repeat itself and no party secures a majority, the election could result in another hung parliament.

In June 2017, a shock exit poll showed Theresa May’s ruling Conservative party had failed to return a parliamentary majority.

It forced the prime minister to strike a deal with the Northern Irish Democratic Unionist Party, or DUP, in order to secure a working majority in the House of Commons.

If there is no clear winner this time around, parties could look to create a formal alliance together. That way, they can bolster their chances of securing enough votes to pass laws in parliament.

Boris Johnson, as the incumbent, would get first try to form a government. Instead of Theresa May’s agreement with the DUP, he could try to secure a formal coalition arrangement, which is what happened in 2010 between the Conservatives and the Liberal Democrats (10).

If Johnson is unable to form a government, he could resign and recommend the leader of the largest opposition party be given a chance to form the executive.

As is typical with major national parties in campaign mode ahead of the general election, they have all suggested they would not be willing to work together to form a government.

Most countries use a proportional voting system, meaning a party that wins half of the total vote share also wins half of the seats in parliament.

But, not in the UK. The voting system used in Westminster is known as first-past-the-post.

A term used in horse racing; it signifies that the contest is effectively over once a candidate receives the largest number of votes for their local area. Essentially, its winner takes all.

The same voting system is used in the United States, Canada and India, as well as many Caribbean and African states.

Advocates of first-past-the-post say it is a simple and familiar process which usually delivers a one-party government. That allows that party to implement their plans over the next five years.

In most constituencies, the majority of people actually end up voting against the winning candidate rather than for them. MPs are sometimes elected on a vote share as low as 35 percent, leaving the losing parties with 65 percent of the vote.

The winning party is also usually elected by less than half of the electorate. In fact, of the 21 general elections between 1935 and 2017, the majority of voters only voted for parties that formed the government on two separate occasions.

Smaller parties often hit out at the first-past-the-post voting system too, arguing they do not gain fair representation. In 2015, the U.K.Independence Party, led at the time by Brexit proponent Nigel Farage, received 12.6 percent, but this only returned one 1 MP.

It is also argued that the first-past-the-post voting system encourages what’s known as tactical voting.

Take so-called ‘safe seats’ for instance. If you’re a voter that lives in a constituency that usually returns a Labour MP for example, you may feel there is little point in backing a Conservative candidate because they are unlikely to be elected.

When this happens — and it happens a lot — voters may choose to vote against a candidate they dislike rather than for one they prefer. Or they might not vote at all. Around two-thirds of constituencies in the UK are considered safe seats.

In 2011, the British public was given a chance to change Westminster’s voting system with the Alternative Vote referendum — but the electorate overwhelmingly rejected this option.

The vote on December 12 is most likely to usher in a government led by either the Conservative Party’s Boris Johnson or the Labour party’s Jeremy Corbyn.

The incumbent has sought to frame the vote as “a Brexit election,” with each of the major national parties offering markedly different visions of how best to resolve the U.K.’s long-running constitutional crisis.

Johnson, who had promised to deliver Brexit by October 31 “come what may, do or die,” demanded a general election after parliament frustrated his attempts to ratify his last-minute divorce deal with the EU.

As the leader of the center-right Conservatives, Johnson said that if his party wins, he will get lawmakers to ratify his Brexit divorce deal before the end of January.

By comparison, Corbyn’s Labour party has indicated they would need slightly longer to resolve Brexit.

The center-left opposition has said it will negotiate a new withdrawal agreement with the bloc within six months of the election. Labour would then seek to hold a national referendum on whether to leave on the terms it has agreed — which it says will mean maintaining very close ties between Britain and the EU — or to remain.

Corbyn, the veteran socialist leader of Labour, hasn’t said which side he would support in such a referendum. (15) Instead, he has argued it is right to try to appeal to both the 52 percent of people who voted Brexit and the 48.1 percent of people that voted to remain.

Meanwhile, the pro EU Liberal Democrats are trying to woo voters away from bigger parties by promising to scrap Brexit altogether. Jo Swinson, the leader of the centrist party, has said the fast-approaching vote is “a moment for seismic change.”

Almost all politicians are in agreement that a pre-Christmas election was necessary to break a cycle of inaction over Brexit.

And major parties are now scrambling to attract weary voters in a bid to end years of political crisis.