U.K. lawmakers will on Tuesday try to stop Prime Minister Boris Johnson from pursuing what they cast as a calamitous no-deal Brexit, a challenge a senior government source said would prompt him to call for a snap election on Oct. 14.

More than three years since the United Kingdom voted to leave the European Union in a referendum, the outcome of the Brexit crisis remains uncertain with a range of options, from a turbulent no-deal exit to abandoning the entire endeavour.

Johnson implicitly warned lawmakers on Monday he would seek an election if they tied his hands, ruling out ever countenancing a further delay to Brexit, scheduled for Oct. 31.

That sets up a historic Brexit showdown between the prime minister and Parliament in a country once touted as a confident pillar of Western economic and political stability. Sterling flirted with some of the lowest levels since 1985.

An alliance of opposition lawmakers and rebels in Johnson’s Conservative Party will use Parliament’s first day back from its summer break to launch their attempt to block a no-deal exit. They are confident of victory.

“I think we will have the numbers,” said one of the rebels, Conservative former finance minister Philip Hammond. “Prime Minister Johnson has always intended that there will be an election.”

Britain’s Labour Party leader Jeremy Corbyn leaves his home in London on Tuesday. Corbyn was scheduled to hold a meeting of opposition parties. (Simon Dawson/Reuters)

In the eye of the Brexit maelstrom, it was unclear whether the rebels, if they defeat the government, would also vote for a snap election, which would require the support of two-thirds of lawmakers. Opposition Labour Party leader Jeremy Corbyn has repeatedly said he wants one.

An option under consideration by Labour would be to support an election, but with some mechanism that would ensure a delay to Brexit, said the Sun’s political editor, Tom Newton Dunn.

‘The country has to come before the party’

The pound, which has gyrated to the rhetoric of Brexit since the 2016 referendum, fell to as low as $1.1959 US. Barring the October 2016 “flash crash” when sterling momentarily tanked to as low as $1.15, the pound has not regularly traded at these levels since 1985.

The Brexit referendum showed a United Kingdom divided about much more than the European Union, and has fuelled soul searching about everything from secession and immigration, to capitalism, empire and modern Britishness.

It has also triggered civil war inside both of the main political parties as dozens of lawmakers put what they see as the United Kingdom’s fate above that of party loyalty.

As Johnson played Brexit chess with lawmakers, opponents cast his order to suspend Parliament as undemocratic and his threat to kick rebels out of the party as a perilous act that could endanger the future of the Conservative Party.

“The country has to come before the party,” Conservative lawmaker Dominic Grieve told LBC radio.

The rebel alliance will put forward a vote on Tuesday on whether to seize control of the parliamentary agenda the following day to try to pass legislation that would force Johnson to seek a three-month delay to Britain’s EU exit.

Mid-October election?

Johnson raised the stakes, however, effectively turning it into a confidence vote by making it clear that if the government were defeated, it would hold a vote on Wednesday to approve an early election, most likely to be held on Oct. 14.

While the British leader said he did not want a snap election, he raised the prospect of one, and a senior government source said lawmakers should be aware it would be a consequence of their decision to vote against the government on Tuesday.

“I don’t want an election. You don’t want an election. Let’s get on with the people’s agenda,” Johnson said at a hastily organized appearance outside 10 Downing Street.

Johnson has cast rebels as EU “collaborators” who are undermining the government’s negotiating hand by blunting his threat of a no-deal Brexit. Johnson’s foreign minister, Dominic Raab, criticized “shenanigans in Parliament.”

Boris Johnson has ruled out ever asking the European Union to delay Britain’s departure from the bloc, making an implicit warning that he would be forced to call an election if British lawmakers tied his hands on Brexit. 2:02

Rebels say the government wants an election, but is trying to blame lawmakers for triggering one.

To hold an election, the government would need the backing of two-thirds of lawmakers in the 650-seat House of Commons. Labour’s Corbyn will host a meeting of opposition parties on Tuesday to discuss their plans to block a no-deal.

Johnson, whose Conservatives have seen an opinion poll bounce since he took office, has a working majority of just one seat in the 650-seat lower house of Parliament.

An election could make a no-deal Brexit more likely, according to JPMorgan, as polling indicates Johnson could win.

“The effect of these developments, in our view, is to push up the probability of a general election occurring next month, and thereby to make no-deal more likely as of end October,” JPMorgan said in a note to clients.