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Boris Johnson is battling to sell his new Brexit deal to skeptical members of the U.K. Parliament ahead of a crucial vote on Saturday.

The prime minister has no majority in the House of Commons but needs to convince his own Conservatives, as well as opposition politicians, to back the divorce accord he struck with the EU on Thursday. If he fails, he will face the choice of seeking to delay Brexit again or trying to take the country out of the bloc without a deal on Oct. 31.

“This is our chance in the U.K. as democrats to get Brexit done,” Johnson told a press conference in Brussels on Thursday. “People want to move this thing on, it’s been going on for a long time.”

He wouldn’t be drawn on what he would he do if he loses Saturday’s vote.

Defeat could unleash a political crisis unparalleled in modern times: despite EU leaders leaving open the possibility of allowing Britain more time to leave, Johnson has repeatedly refused to contemplate delaying Brexit beyond Oct. 31. Any attempt to leave without a deal would face a legal challenge and he may have to allow his plans to be tested in a general election or even a second referendum.

The parliamentary arithmetic is very tight. Johnson is trying to win Saturday’s vote without the support of Northern Ireland’s Democratic Unionist Party, which has categorically rejected the agreement he reached with the EU. To get the votes he needs, the premier is wooing reluctant members of his own side and trying to persuade opposition Labour politicians to back him.

Former Conservative MPs who voted to block Johnson’s threat of a no-deal divorce last month -- and were thrown out of the party as a result -- have proposed an amendment to Saturday’s motion that seeks to force the government to request a delay to Brexit until a deal is passed.

Under Johnson’s plan, Northern Ireland would still be subject to some of the EU’s single market rules to mitigate the need for customs checks on the border with Ireland. That would, in effect, put a customs border in the Irish Sea. The DUP says this is completely unacceptable and its 10 MPs will vote against.

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Will U.K. Parliament Back Boris Johnson’s Brexit? We Do the Math

To win, Johnson needs to pick up roughly 61 votes from a pool of about 75 Members of Parliament who might be persuaded to join him.

There are signs that some Tories who voted down his predecessor Theresa May’s deal -- among them Steve Baker, leader of the self-described “Spartan” group of hard-core Brexiters -- are falling into line. But the DUP’s Sammy Wilson told the BBC on Friday that he and colleagues are urging the Spartans to stand with them.

Johnson is also trying to win the support of a significant minority of MPs from the opposition Labour Party who believe the 2016 referendum result must be honored. To woo them, he is preparing a package of measures, including protections for workers’ rights and environmental standards after Brexit.

Labour leader Jeremy Corbyn called for a second referendum, saying Johnson’s deal -- which he described as a “sell-out” -- is worse than that put forward by May. But there are some of his MPs who may still back it. “It’s a bad deal, but if I thought we wouldn’t get Brexit at all, then I would consider voting for it,” one Labour MP, Graham Stringer, told the BBC.

Scotland’s first minister, Nicola Sturgeon, said her Scottish National Party will vote against the deal, complaining that it creates too great a separation from the EU.

As attention swung toward the vote at Westminster, European Commission President Jean-Claude Juncker offered support to Johnson.

“If we have a deal, we have a deal and there is no need for prolongation -- that’s not only the British view, that’s my view too,” Juncker said. “He and myself we don’t think that it’s possible to give another prolongation.”

Even if the decision over whether to grant an extension is not his, by playing down the chances of another delay, Juncker helped frame the vote in the House of Commons as a straight choice between Johnson’s deal or no deal -- just as the British leader has tried to do himself.

That increases the pressure on undecided lawmakers in Westminster to back the government -- but it also raises the cost of failure dramatically.

(Updates with DUP urging Tories to stand with them in ninth paragraph.)

--With assistance from Ian Wishart, Jonathan Stearns, Viktoria Dendrinou, Nikos Chrysoloras, Helene Fouquet, Patrick Donahue, Dara Doyle, John Follain, Katharina Rosskopf, Tiago Ramos Alfaro, Milda Seputyte, Jan Bratanic and Robert Hutton.

To contact the reporters on this story: Tim Ross in London at tross54@bloomberg.net;Kitty Donaldson in London at kdonaldson1@bloomberg.net

To contact the editors responsible for this story: Tim Ross at tross54@bloomberg.net, Thomas Penny, Andrew Atkinson

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