Boris Johnson’s resignation as foreign secretary yesterday made him the third minister in 24 hours to walk out of the government in protest at UK Prime Minister Theresa May’s proposals for a “soft Brexit,” i.e., maintaining access to the European Union’s (EU’s) Single European Market, at least regarding goods.

Following the resignations of Brexit Secretary David Davis and his junior minister, Steve Baker, Johnson’s exit has fuelled speculation that more desertions might follow, triggering a Conservative Party leadership contest.

Opinion is divided. Some believe that May still enjoys a parliamentary majority in a deeply divided parliamentary party because she can secure support on both sides of the divide over Brexit, which leaves champions of a hard-Brexit (leaving Britain outside the Single European Market) concerned to not jump too soon.

Johnson himself, while describing May’s proposals as “a turd,” initially agreed to support them but was forced to resign after Davis quit to maintain his credibility among the Brexiteers.

Unlike Davis, who stressed that he remained loyal to May, Johnson quit in a manner designed to inflict maximum damage to the prime minister. His resignation was announced as May’s deputy, David Lidington, was briefing opposition Labour MPs on the details of May’s proposals, and just half an hour before she was due to address the House of Commons.

Johnson himself was due to host a summit on the western Balkans but was a no-show, without offering any explanation. Speaking for the ministers from the six western Balkan countries as well as Austria, France and Poland, Germany’s Europe minister, Michael Roth, tweeted, “We’re still waiting for our host. ...”

Johnson’s resignation letter, released later that day, was scathing. He had tried to support the line agreed at the PM’s country residence at Chequers Friday, but, “The trouble is that I have practised the words over the weekend and find that they stick in the throat.” May’s plan amounted to “a semi-Brexit,” he declared.

May’s trump card is the concern that her departure will make more likely an early general election and a Labour victory under Jeremy Corbyn, despite the provisions for fixed-term parliaments introduced by May’s predecessor, David Cameron. This is regarded as a disastrous outcome throughout the Tory Party, and nowhere more than on its hard-Brexit wing.

The Fixed-Term Parliaments Act requires a motion agreed by two thirds of all MPs if a no-confidence motion is passed and no alternative government is put forward within 14 days.

A poll conducted by for the Independent saw Labour now two points ahead of the Tories. The survey by Survation of 1,007 adults found Labour at 40 percent and the Tories down three points to 38.

Also damaging for May, an online poll of Tory members by the Conservative Home website found that 61 percent of respondents said her proposal would be a bad deal for Britain, compared to just 31 percent who thought it would be good.

Aside from May’s resignation, a leadership contest requires 15 percent of Tory MPs, 48, to write letters of no confidence to Graham Brady, the chair of the 1922 Committee of backbench MPs. Should May lose a vote of no confidence, a spokesperson for May said that she would take part in any leadership contest.

After appearing before the Commons, May addressed backbench Tory MPs for an hour, during which she focused on warning hard-line Brexiteers that they were risking handing power to Corbyn. A cabinet member summarised her message as, “If we don’t pull together, we risk the election of Jeremy Corbyn as prime minister. … At least half a dozen people made that point and the prime minister responded—what is good for the country is a Conservative government.”

Earlier, one “senior Brexiteer” told the Guardian, “They’ll keep going, one by one, until she either junks [her proposals agreed at] Chequers, or goes.” Another told the Independent that their concerns were with “policy, not personnel.” But whatever happens next, May’s position is rapidly becoming untenable.

There has been no indication from the EU that it will accept her proposal for the UK to levy tariffs on goods at its own rate and then collect a higher rate only for those goods transiting to Europe—as a means of avoiding the commitments accompanying full membership of the Single European Market, including free movement of labour.

Even if a climb-down is reached, May will probably need at least some support from within the Labour Party given an almost inevitable rebellion by hard-Brexit Tories. A no-agreement Brexit at the conclusion of the UK/EU negotiations would almost certainly lead to May’s downfall.

Shadow Brexit Secretary Sir Keir Starmer has said that Labour will not support leaving the EU in eight months’ time based on May’s proposals and will demand a parliamentary vote to be followed by a “people’s vote.”

Corbyn has previously stressed that a general election should be held in eight months but is now calling for an earlier poll.

Prior to May addressing parliament, he tweeted, “David Davis resigning at such a crucial time shows Theresa May has no authority left and is incapable of delivering Brexit. With her Government in chaos, if she clings on, it’s clear she’s more interested in hanging on for her own sake than serving the people of our country.”

Shadow Chancellor John McDonnell said, “With a prime minister incapable of holding her ministerial team together and with such instability in government it’s impossible to see how EU leaders could take Theresa May seriously in the next round of negotiations. It’s time for her and her party to put country before party and go.”

Labour is competing with the Tories largely on the basis that it is better placed to safeguard business interests that are heavily dependent on access to European markets—which account for up to 40 percent of Britain’s exports—and which are also essential in maintaining the City of London as a global financial centre.

Johnson and the hard-Brexiteers, as well as May to a lesser extent, are calculating that the EU can be pressured to make far greater concessions than appears likely now.

This is based on factors including Britain’s strategic military and security role, but most importantly, by forging an alliance with US President Donald Trump and backing his insistence that the EU open up its markets. Woody Johnson, recently appointed US ambassador to Britain by Trump, intervened directly in support of Davis and Johnson, telling the BBC that the chances of the two countries reaching a trade deal after Brexit were “up in the air at this point,” following the Chequers agreement. Trump ”would love to” strike a deal with the UK because he “respects sovereignty,” he added.