On April 18, British Prime Minister Theresa May called for an early general election, bumping it up from 2020. British voters are set to cast their ballots for the House of Commons' 650 seats on June 8. Brexit will likely dominate the campaign agenda, with many perceiving the election as a vote on May's Brexit leadership.

Though May had previously denied she would call for an early ballot, she argued snap elections were now necessary to counter the opposition's "political game-playing" on the UK's departure from the European Union (EU). For May, who took office after David Cameron resigned in the wake of the Brexit referendum, the vote marks her first attempt to secure a popular mandate.

With the opposition at its weakest position in years, the early election will likely prove a major boon to the Tories, allowing them to comfortably expand their current 17-seat majority in the House of Commons. Overall, the Conservatives have backed May's leadership as she steers the UK towards a hard Brexit, which includes removing the country from the European single market.

Embattled Labour leader Jeremy Corbyn announced his support of May's call for snap elections. He will attempt to position his party as an "effective alternative" to the Tories. Corbyn, a traditional labourist, will campaign on reversing government austerity, nationalizing railways, and investing in wages, all while steering clear of Brexit so as to not alienate the party's pro-leavers.

Analysts predict few election gains for Labour, however, as Corbyn's Old Labour policies and refusal to bend to backbench opposition have split the party. Some Labour MPs challenged his support of snap election, and Labour MP Tom Blenkinsop said he would not stand for re-election due to "irreconcilable differences" with Corbyn.

Tim Farron, current leader of the Liberal Democrats said that, "only the Liberal Democrats can prevent a Conservative majority." After the party's coalition with the Conservatives under Cameron, the Lib Dems were smashed in 2015 national elections, receiving only nine seats. For Farron, the snap election will be a chance for him to significantly build up his party's representation in parliament.

The pro-EU and economically liberal party also used May's announcement to call for a second Brexit referendum. In terms of the June elections, the Lib Dems could benefit from disaffected pro-EU Labour voters and those who seek a "soft Brexit" that would keep the UK in the European single market. According to the party, 1,000 people registered as Lib Dems just after May's announcement.

Like the Lib Dems' Farron, first minister of the Scottish government and Scottish National Party leader Nicola Sturgeon clearly positioned herself against May, describing the Prime Minister's move as a "huge political miscalculation." May and Sturgeon have been a loggerheads over whether or not a second Scottish referendum can go forward before Brexit comes into effect.

The SNP already holds 54 of Scotland's allotted 59 MP seats, leaving little room for gain. However, the party is also unlikely to lose seats as their support has stayed steady. A majority of Scots voted to remain in the EU, meaning that Sturgeon could frame the election as both a call to Downing Street to consider a "soft Brexit" option and to consult the devolved nations in exit negotiations.

Despite being a major player in the campaign to take the UK out of the EU, the UK Independence Party (UKIP) currently has just one seat in parliament. However, the Euroskeptic party still has a support base, and leader Paul Nuttall will seek to paint May as a political opportunist. Yet this will not likely translate into seats as many former UKIP voters have joined May's "hard Brexit" bandwagon.

Other parties currently holding Commons' seats include the Greens (one), Northern Ireland's Democratic Unionist Party (eight) and Sinn Fein (four), as well as Wales' Plaid Cymru (three). The June 8 election date places the UK's national election between that of France (April/May) and Germany (September), meaning parliamentary chambers on both sides of the channel may be in for a shake up.

Article 50 of the Treaty of Lisbon gives any existing member of the European Union the right to quit unilaterally and outlines the procedure for doing so. It gives the state concerned two years to negotiate a deal for its exit. Once Article 50 is triggered, it cannot be stopped, except by the unanimous consent of all member states.

There are five elements in Article 50. They state that the exiting country must notify the European Council formally and that it is given a two-year period to reach an agreement. Article 50 also states that the country concerned cannot take part in EU’s internal discussions about its departure. The exit deal must be approved by a "qualified majority" and must also get the backing of MEPs.

The UK decided in favor of leaving the EU in a referendum in June 2016. After lengthy parliamentary debates and legal procedures, Prime Minister Theresa May looks all set to send a formal letter of notification to EU President Donald Tusk on March 29, which will trigger Article 50. Officials in Brussels have already outlined a divorce bill for Britain of between 55 and 60 billion euros.

The EU is expected to give a first response later this week. A summit of EU leaders on April 29 is then to lay down guidelines for the Brexit talks, which are expected to start in May or June. The hardest part of the negotiations will be determining the status of more than a million Britons living in other parts of the EU and of some 3 million EU citizens in Britain, and working out trade details.

By autumn this year, the UK government is expected to introduce legislation to leave the EU and put all existing EU laws into British law - the Great Repeal Bill. The possible move will annul the 1972 European Communities Act (ECA), which gives EU law instant effect in the UK, and give parliament the power to absorb parts of EU legislation into UK law, scrapping elements it does not want to keep.

EU leaders have said they want to conclude the talks within 18 months to allow the terms of the exit to be ratified by UK and the European Parliaments as well as the EU states. If no agreement is reached in two years and no extension is agreed, the UK automatically leaves the EU and all existing agreements.

The fifth paragraph of Article 50 raises the possibility of a state wanting to rejoin the EU after having left it. This would be considered under Article 49.