LONDON — After Theresa May's three failed attempts to win over lawmakers, current U.K. leader Boris Johnson will put his own Brexit deal to the test during a historic Saturday sitting of the British Parliament.
The House of Commons began sitting from 9.30 a.m. London time and will continue "until any hour," according to the latest agenda paper. The House is sitting on a Saturday for the first time since 1982, when the U.K. was at war with Argentina.
Addressing the House prior to the vote Saturday morning, Johnson said the new deal "allows the UK whole and entire to leave the EU on October 31 in accordance with the referendum whilst simultaneously looking forward to a new partnership based on the closest ties of friendship and cooperation."
"This agreement provides for a real Brexit, taking back control of our borders, laws, money, farming, fisheries and trade. It is the greatest single restoration of national sovereignty in parliamentary history," the prime minister added.
Aside from key changes in how Northern Ireland is treated, there appears to be little difference from May's failed deal, but Johnson will be banking that lawmakers, tired of the Brexit deadlock, will switch to support his withdrawal deal.
Some reports suggest Johnson has persuaded hardline Brexiteers that by voting for his deal, the government can keep the threat of a no-deal on the table when trade negotiations begin during the Brexit transition period.
Responding to Johnson's opening remarks, main opposition Labour Party leader Jeremy Corbyn said the new deal "risks people's jobs, rights at work, our environment and our National Health Service."
"We must be honest about what this deal means for our manufacturing industry and people's jobs. Not only does it reduce access to the market of our biggest trading partner, it leaves us without a customs union which will damage industries all across this country in every one of our constituencies," Corbyn added.
Corbyn also said the new arrangements would inevitably lead to a trade deal with the Trump administration, "forcing the U.K. to diverge from the highest standards and expose our families once again to chlorine-washed chicken and hormone-treated beef."
Johnson will take at least 90 minutes of questions about his talks that led to the agreement between the U.K. and 27 other EU leaders.
Amendments to the vote have been made possible by a Commons victory on Thursday which saw remain MPs and opponents to a no-deal Brexit vote in unison. If any amendment is selected by the Speaker of the House John Bercow and approved by lawmakers, it could mean the outcome of Saturday's vote is altered significantly.
One possibility is a stiffening of existing legislation that prevents no deal at all, while another possible vote is on whether a second public referendum is needed to confirm Johnson's Brexit deal. The most significant of these is the "Letwin amendment" which would withhold approval of the deal until the legislation is in place to enact it.
By proxy, this would activate the "Benn Act" forcing the prime minister to request an extension to the October 31 deadline. Meanwhile, Sky News has reported, citing a source from Downing Street, as suggesting the government will sit out the vote on the deal, effectively cancelling it, should the Letwin amendment pass. CNBC has not been independently verify this information.
The Letwin amendment is expected to curry favor with MPs who want a deal but do not trust the current government to avoid a no-deal exit by enacting the Benn Act properly.
In the afternoon, the government motion is expected to ask lawmakers to approve the deal. The vote is expected to be tight with more "hard Brexit" supporters in his Conservative Party now ready to back Johnson after rejecting May.
If MPs (Members of Parliament) do approve the deal unamended on Saturday, the government is expected to table the Withdrawal Agreement Bill as soon as Monday, freeing the U.K. to leave the European Union on October 31.
The U.K. then enters into a transition period until the end of 2020. During this time, the EU and U.K. would attempt to resolve future trading terms.
Should Johnson lose the vote, U.K. legislation means he has until 11 p.m. London time to send Brussels a letter requesting an extension to the Brexit deadline.
The prime minister needs roughly 318 votes to pass the motion, but there are only 288 Conservative Party MPs.
On these calculations, which assumes all Conservatives vote for the deal, Johnson is 30 votes short.
His former reliance on 10 votes from the Democratic Unionist Party (DUP) has now evaporated with the Northern Irish party, angry at the deal struck with Europe, now vowing to oppose the government.
Further opposition can be expected from the Scottish National Party (SNP), Plaid Cymru (Welsh national party), Liberal Democrats, one Green Party MP and of course, the main rump of the opposition Labour Party.
But all is not lost for Johnson and there are three sources he can plunder for support:
Some pro-deal Labour MPs have already confirmed they will defy their party to vote with Johnson while, conversely, some rebel Conservative lawmakers are set to reject Johnson's proposal.