British prime minister Theresa May is about to take a huge political gamble.  She has called for general elections at the earliest possible moment – in this case, June 8.

May is looking for a larger conservative majority to be able to implement her Brexit plan.  Stiff opposition in Parliament has threatened to derail the entire Brexit process, so May felt she had little choice but to call for a new vote.

BBC:

"I have only recently and reluctantly come to this conclusion. Since I became prime minister I've said there should be no election until 2020, but now I have concluded that the only way to guarantee certainty and security for the years ahead is to hold this election and seek your support for the decisions we must take."

In a statement outside Number 10, Mrs May said Labour had threatened to vote against the final Brexit agreement, the Liberal Democrats had stated they wanted to "grind the business of government to a standstill", the SNP have said they would vote against the legislation that formally repeals Britain's membership of the EU – and "unelected" members of the House of Lords had vowed "to fight us every step of the way".

"If we don't hold a general election now, their political game-playing will continue and the negotiations with the European Union will reach their most difficult stage in the run up to the next scheduled election," she said.

Polls show that it the election were held today, the Conservatives would maintain their status as the largest political party in Parliament, but their numbers fall short of a majority. 

May had promised to hold no elections until the regularly scheduled vote in 2020.  But circumstances have forced her hand:

For months Theresa May and her team have played down the prospect of an early poll. The reasons were simple. They didn't want to cause instability during Brexit negotiations. They didn't want to go through the technical process of getting round the Fixed Term Parliaments Act.

They didn't want the unpredictability of an election race. And many in the Conservative Party believed there is so little chance of the Labour Party getting its act together before 2020 that they could carry on until then and still expect a sizeable majority.

There was also, for Theresa May, the desire to show that she will be a prime minister who sticks to her word. But the relentless political logic proved too tempting to hold to all of that.

The PM challenged the opposition parties: "This is your moment to show you mean it - to show you're not opposing the government for the sake of it, to show that you do not treat politics as a game.

"Let us tomorrow vote for an election - let us put forward our plans for Brexit and our alternative programmes for government and then let the people decide.

Much will depend on how May frames the election.  Challenging the opposition to put up or shut up is inherently dangerous to her standing.  A significant loss of her majority could result in the fall of her government.  If that happens, Brexit might be fatally delayed while Great Britain sorts out its politics.

It will be interesting to see how the U.K. Independence Party – UKIP – plays this election.  They are anti-E.U. and anti-immigrant but have given lukewarm support to May.  Their ability to pull votes from the Conservative Party may be crucial to the outcome.