What will happen after the vote on May's Brexit deal?

In all likelihood the PM will be defeated – but the margin of defeat is crucial to what happens next

Nobody at Westminster expects Theresa May to win Tuesday night’s vote on her Brexit deal. But a wide range of outcomes are possible, and they will determine what happens next.

Under an amendment passed by increasingly rebellious MPs last week, May must respond to a defeat within three sitting days – by Monday 21 January. But her Commons statement will not necessarily offer a definitive plan B; she could say she is seeking further negotiations with the EU. The debate and vote on her motion would not have to take place on Monday, giving May a small window for further talks.

What, then, are the most likely outcomes of Tuesday’s vote, and what would follow?

The numbers game

More than 100 Conservative MPs have criticised May’s withdrawal agreement. On paper, if they and the 10 Democratic Unionist Party MPs, all voted against the deal, it would be defeated by around 200 votes. In practice, that will not happen. Some of the Tory critics have reluctantly decided to back the deal; a small number of Labour MPs have pledged support. So has one Liberal Democrat. May’s twin threats of a no-deal exit and “no Brexit” could persuade other critics to back her agreement or abstain.

So May might benefit from the “expectations game” if the defeat does not look so bad on the night.

Crushing defeat

Defeat by more than 100 votes on such a flagship policy would normally see the resignation of a prime minister. But these are not normal times, and May would regard it as her duty to plough on. However, a three-figure margin would be humiliating, and would encourage MPs to try to seize control of the Brexit process – for example, by demanding a series of indicative votes on a possible plan B – including a Final Say referendum; a Norway plus arrangement inside the single market and a customs union; an EU-Canada-style free trade agreement and a “managed no deal”.

Supporters of the different options are keen for their plan to be “the last one still standing” after all the others have been rejected, so much will depend on how such indicative votes were held. If there is no majority for any alternative deal, the prospect of a referendum would increase.

After a crushing defeat, it would be harder for May to claim her deal could be amended and put to a second Commons vote after further EU concessions. The cabinet’s position would be important – although, like backbenchers, ministers are divided between a plan B deal involving a softer Brexit, and those willing to risk a no-deal departure. Ministers might finally call time on May’s deal, and persuade her to stage indicative votes and then adopt whichever came out on top.

May would probably need her own plan B to avoid having one imposed on her by the cabinet or Commons. After surviving a confidence vote as Tory leader last month, her Eurosceptic MPs cannot challenge her for another year. The threat to her is now from parliament. So she might try to build a majority with the votes of Labour MPs – perhaps by embracing a permanent customs union, something she has always opposed.

May could make a “managed no deal” the government’s central policy to honour her pledge to leave the EU on 29 March. But that would provoke cabinet resignations and MPs would likely find a way to block it.

Some ministers expect May to lose by between 70 and 100 votes. She could claim some momentum towards accepting her deal, and go to Brussels to seek improvements. She would probably get one more chance to put a revised deal to the Commons. The EU’s role will be critical in this scenario. EU insiders suggest they will be more flexible once parliament has voted on the deal, and might even reopen the withdrawal agreement. But they would first need to know what MPs would accept.

As good as it gets

Some ministers believe that limiting the losing margin to under 70 votes would show that May’s deal is still alive. It’s the best she can hope for, and the expectations game would work in her favour. She would tell the EU that legally-binding guarantees that the backstop to prevent a hard Irish border is temporary, might secure a Commons majority in a second vote. May would be tempted to repeatedly put her amended deal to MPs until she got over the line.

Health warning

In a series of votes on Tuesday, parliament’s arcane procedures will be very important. Bizarrely, it possible that there is no specific vote on May’s deal, because MPs will first vote on amendments. Hilary Benn, Labour chairman of the Brexit select committee, has tabled one rejecting both a no-deal exit and May’s agreement. If passed, MPs would not vote solely on her deal. Benn is under pressure to withdraw his amendment as, if approved, it could minimise the scale of May’s defeat (as about 50 hardline Brexiteers will not vote against “no deal.”)

The other amendment to watch, tabled by Tory MP Andrew Murrison, would end the Irish backstop after a year in December 2021. Ministers are encouraging Tories to back it. Brussels has refused to put a time limit on the backstop; passing this amendment would put the ball back in the EU’s court.

The amendments, and the order in which they are voted on, will be selected by Commons speaker John Bercow, putting him back in the spotlight, after he was accused of anti-Brexit bias last week.

Delay?

In the Commons today, May repeated her determination not to extend the two-year Article 50 process beyond 29 March. However, she might be forced to rethink once her deal is rejected. Even if she salvaged it in later votes, time would be running out to push through key legislation needed by exit day. MPs are likely to vote for the government to ask the EU to extend the time limit – not least to head off a cliff-edge departure.

Although much of what happens next is shrouded in uncertainty, there is one good bet: an extension of Article 50.