London (CNN) The UK Parliament will vote Friday on Theresa May's Brexit deal for a third and possibly final time, the British government confirmed. But the arrangements are, unsurprisingly, mired in confusion and controversy.

Andrea Leadsom, leader of the House of Commons, told lawmakers that the government had decided to split the Withdrawal Agreement -- which sets the divorce terms -- from its associated Political Declaration, which deals with the future relationship between the UK and the European Union.

That split has enraged opposition Labour lawmakers -- and some Conservatives -- who think it contravenes the European Union (Withdrawal) Act 2018, which demands that the whole thing be ratified together.

Legal or not -- frankly, that debate is a sideshow -- the vote will take place tomorrow. A more pertinent question is whether it will pass. To turn over a parliamentary loss of 149 in two weeks that not much has changed is a huge ask for any leader.

Sure, the Prime Minister's game-changing announcement on Wednesday that she will stand down if her deal is approved by parliament this week earned her some immediate wins. The decision by former Foreign Secretary and arch-Brexiteer Boris Johnson to back her deal is no small thing. But it might not be enough.

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