Tonight's vote on Theresa May’s Brexit deal is one of the most-anticipated Commons events in years. The result - and the scale of it - will trigger one or several of a series of outcomes. Here are some of the possible scenarios.
The most straightforward, if unlikely, result of the vote. Should May somehow tempt enough rebels back to her view and prevail, then there would be an agreed departure deal with which the EU could work, and it would be full steam ahead to 29 March. Yes, there would be more fierce and endless arguments on everything from the backstop to the future trade deal, but the basics would be there.
May loses and pledges to try again
Barring a particularly big defeat for the prime minister, this is what many MPs believe would come next – May makes a rapid statement saying she would go back to Brussels and seek more concessions, notably on the backstop. The thinking has been that once the EU has seen the concrete evidence of MPs’ views they would be more likely to come up with something genuinely new, to try to avoid no deal. Those being most targeted for a change of heart would be the Democratic Unionist party, Tory waverers and Labour MPs from leave-minded seats.
Article 50 is extended
Seen as a necessary adjunct to the above tactic – and perhaps needed in just about any scenario – this has now been unofficially promised by the EU. The most likely variant would be a “technical” extension until July or thereabouts, to allow more time for a second vote, and to pass other Brexit-related legislation. But if there was something new afoot, whether an election or a second referendum, a longer timetable still could be offered.
May loses and a plan B emerges
Some Conservative MPs predict that, if the margin of defeat was heavy, May might finally decide – or be persuaded – to drop her long-held plan, seek an extension to article 50 and embark on a cross-party push for a more consensual Brexit, perhaps based on a Norway model. Given how vehemently and how often the PM has rejected such a course it seems unlikely. More possible, though still marginal, would be the idea of backbenchers using parliamentary procedure to effectively take control.
The men in grey suits pay a visit
Some speculation centres around the idea of a particularly heavy defeat seeing May pledging to plough on, at which point her colleagues act. They cannot formally remove her until December, as her win in the Tory MPs’ confidence vote before Christmas keeps her officially safe for a year, so instead the scenario has a delegation of cabinet ministers going to No 10 and telling the PM her time was up. She could well send them packing.
A general election
This has been the favoured Labour approach if May loses her Brexit vote. Under the Fixed-term Parliaments Act, a specifically-worded no-confidence motion against the government would be debated and voted for or against relatively soon. If lost, there would be a 14-day period for a new government to be formed, but if this could not happen then an election would be called. However, while a number of Tories were likely to vote against May’s deal, it was another matter to ask them to vote down their government. Another option, which some Labour MPs have been privately wary about, was the idea of May deciding to call an election herself, gambling that she might be able to present a more coherent Brexit approach than Jeremy Corbyn.
This has been the hope of a good number of Conservative and Labour MPs, supported by the energetic People’s Vote campaign, but has been vehemently opposed by May and others in parliament. Many argue that the most likely way to bring about a second referendum would be if Labour formally threw its weight behind the idea. However, Corbyn has made it plain that his preferred route would be to negotiate a different Brexit deal.
This has been simultaneously the default option – if May’s deal was lost and nothing has been put into its place, then a no-deal departure would happen automatically on 29 March – and also something discounted as impossible by many MPs. The decision of the Commons last week to back an amendment to the finance bill tabled by Labour’s Yvette Cooper seeking to block no deal has relatively little actual power, but shows the arithmetic in parliament supports such an approach. Several Tories have also vowed to quit ministerial jobs or even the party whip if no deal became policy. All that said, as many commentators have noted, many events in history not actively sought by the majority have still happened because not enough people took action to prevent them.