British Prime Minister Theresa May speaks to the media outside 10 Downing Street in London on April 18. (Stefan Wermuth/Reuters)

British Prime Minister Theresa May announced Tuesday that she wants to hold a snap general election in June, catching Britain and the world by surprise on several levels. Not only had May previously ruled out an early vote, but some legal observers had said that such a move would go against the intentions of British electoral law.

For decades, Britain's prime ministers have held almost unchallenged powers to call early elections, but critics say snap elections have mainly been used by British leaders to hold early votes when it benefited their own parties. In response to that criticism, the then-ruling coalition of Conservatives and Liberal Democrats passed the Fixed-Term Parliaments Act in 2011 to prevent future snap elections from being used as a political tool. Under that law, general elections are supposed to be held on a regular five-year schedule, with the next vote due in 2020.

Technically, there are now only two ways to call early elections. The House of Commons can pave the way for an early vote by approving it with a two-thirds majority, or it can defeat the prime minister in a vote of confidence and have that result stand for two weeks.

Most members of the Liberal Democrats as well as the Labour Party are expected to vote in favor of May's plans. The Liberal Democrats perceive the vote as a chance to win over voters opposed to leaving the E.U. The reasons for the Labour Party to support new elections are less clear, but Jeremy Corbyn, the unpopular Labour leader, has already vowed to back May's plan.

But the early election is still a politically charged issue. By holding an early vote, May would give herself more time to deal with post-Brexit fallout — the 2020 vote would fall one year after the country is set to leave the E.U. — as well as a potentially stronger mandate during negotiations.

In a surprise announcement, Britain's prime minister called for an early election on June 8. (The Washington Post)

In the latest YouGov poll, May's Conservative Party has a 21 percent lead over the Labour Party, its main opposition, and an even larger advantage over the pro-Europe Liberal Democrats. The Conservative Party could expand its majority if there are no unforeseen changes in public opinion over the next two months, providing May with much more leeway to pass a Brexit deal without having to make concessions to other British parties.

May herself made references to the upcoming Brexit negotiations during her announcement. “Our opponents believe because the government’s majority is so small that our resolve will weaken and that they can force us to change course,” May explained Tuesday in front of 10 Downing Street.

A person holds a Union Jack flag during a demonstration near the British Parliament on March 29 in London. (Carl Court/Getty Images)

“At this moment of enormous national significance there should be unity here in Westminster, but instead there is division. The country is coming together but Westminster is not,” she said, referring to the British Parliament.

No wonder that several Labour members of Parliament said they were shocked by the snap election plans, fearing that the early vote will only benefit the prime minister. May's comments, they argue, clearly implied that the real purpose of an early election was to silence her critics in Parliament.

Read more: 

Britain’s snap elections won’t reverse Brexit. Here’s why.

British prime minister calls for elections in June amid Brexit fallout