We examine the possible scenarios, from a snap election to a second referendum

What happens next if Theresa May's Brexit deal is voted down?

After taking her Brexit deal on a round-Britain roadshow last week, Theresa May is spending much of the next few days holding face-to-face meetings with her MPs in an attempt to persuade them to support it in the meaningful vote on 11 December.

But with the parliamentary arithmetic looking bleak, just about everyone in Westminster is busy looking beyond next Tuesday – and puzzling over what will happen next.

If the deal is voted down as anticipated, there are at least seven possible scenarios:

1. May switches to plan B

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While no one in Downing Street wants to countenance it openly, the EU Withdrawal Act – as amended by MPs – gives Theresa May up to 21 days to return to parliament and set out what she plans to do next.

She could come back to parliament and say she will seek to renegotiate the backstop – though No 10 insists that would be impossible – or even pivot towards a different kind of Brexit, perhaps with a permanent customs union as Labour is calling for.

May could also ask for an extension to article 50, the strictly time-limited EU exit procedure, in order to allow her to renegotiate, though that would require the consent of all 27 other EU member states.

2. She calls a snap general election

Rumours have been swirling around Westminster for several weeks now, suggesting Downing Street could choose to take a dramatic gamble and appeal to the public, over the heads of squabbling MPs, to back the prime minister’s deal.

Of course, it did not go too well the last time she asked voters to give her a fresh Brexit mandate, last year, but internal polling suggests there is considerable personal sympathy for the embattled prime minister. If she won, she could press ahead with her deal.

Under the Fixed-term Parliaments Act, she would need a two-thirds majority to trigger a general election, but last year’s experience suggested that is not an insurmountable barrier – and Labour is champing at the bit.

Parliament must be dissolved at least 25 working days before a general election can be held, so any election would probably take place in late January.

3. May resigns

The prime minister has been so intimately associated with the shape of this Brexit deal, with its focus on controlling migration and extricating Britain from the scope of the European court of justice, that a heavy defeat could fatally undermine her already dented authority.

Particularly if the defeat is a hefty one, she may decide she cannot be the person to make the next move – or her cabinet may decide for her.

The Conservatives would then need to hold a hasty leadership contest, the outcome of which could have a profound impact on the shape of Brexit.

4. Conservative MPs dump May

If May opts to try to cling to office after a thumping defeat in the meaningful vote – and her cabinet does not show her the door by threatening to resign en masse – she could face a vote of no confidence in her leadership.

The European Research Group of Brexiters failed to muster the 48 names necessary to trigger such a vote last month, but following a defeat, particularly if May appears unwilling to change course, many more could decide to join them.

Losing the vote would prompt a leadership contest, in which May could not stand, and her successor would face the job of resurrecting Brexit with the 29 March deadline fast approaching.

5. The government falls

Labour’s priority is to try to secure a general election, to allow Jeremy Corbyn to take over and send Sir Keir Starmer to negotiate with Brussels.

In the days following the vote, Labour could table a vote of no confidence in the government. May could still win it, but not without the support of the DUP, which is deeply dissatisfied with her approach to Brexit.

If the government loses, Corbyn would have a fortnight in which to try to assemble a viable governing majority, by teaming up with other parties. If he was unable to do so – which would appear likely – a general election would be called.

Another outlandish possibility being mooted by some at Westminster is that a time-limited, cross-party “government of national unity” could emerge at this point, perhaps around the idea of a Norway-style Brexit.

6. Parliament takes back control

Dominic Grieve and his allies have fought to ensure that whichever motion is brought back to parliament by the government, once the vote has failed, can be amended.

In theory at least, that could allow MPs to test the backing of MPs for a menu of different options, including a harder or a softer Brexit.

Even if a majority emerged for an alternative approach, it is unclear whether such a motion would be formally binding on the government. But proponents of this approach argue that it would have political bite, as a statement of the collective will of the House of Commons.

7. Second referendum

Rebel MPs who support a “people’s vote” are determined to try to use any parliamentary tactics they can to force the government to take its Brexit deal to the public in another referendum.

Crucially, while several on the Labour frontbench remain deeply sceptical about the idea, its membership is overwhelmingly in favour of overturning Brexit, and leading figures including the shadow chancellor, John McDonnell, have begun to make warmer noises about it.

It remains unclear whether there is time for a referendum to be held before the March deadline and an extension of article 50 would probably be necessary.

But if parliament appears deadlocked, passing the question back to the public could look increasingly appealing.