LONDON (Reuters) - Britain leaves the European Union on March 29, yet little is clear: There is, so far, no divorce deal, rivals to Prime Minister Theresa May are circling and some rebels have vowed to vote against a possible Brexit deal.

FILE PHOTO: An anti-Brexit demonstrator waves flags outside the Houses of Parliament, in London, Britain, September 10, 2018. REUTERS/Hannah McKay

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How will the Brexit finale play out?

Following are scenarios:

1) DISORDERLY BREXIT

If May is toppled, fails to reach an agreement with the EU or parliament rejects her deal, Britain would plunge into crisis. Many opponents of Brexit predict this outcome, as do some supporters of a deeper break with the EU than that advocated by the prime minister.

- MAY FALLS

May’s snap election in 2017 lost her party its parliamentary majority. Her minority government is now propped up by 10 Democratic Unionist Party lawmakers from Northern Ireland.

Her Conservative Party, which has been split over Europe for 30 years, is in open conflict and some of her lawmakers want a new leader.

If May fell, selection of a new party leader would delay already tight Brexit negotiations. A national election is possible, though not legally necessary. Opinion polls show no party has a clear enough lead to predict victory confidently.

Poll ratings have fallen for Labour leader Jeremy Corbyn, who voted ‘out’ in a 1975 referendum on membership of the then European Community.

Possible successors to May include former foreign secretary Boris Johnson, interior minister Sajid Javid, environment minister Michael Gove, current Foreign Secretary Jeremy Hunt and Dominic Raab, her Brexit minister.

Other possible contenders include Tom Tugendhat, a former soldier who chairs the parliamentary Foreign Affairs Select Committee, and hardline Brexiteer lawmaker Jacob Rees-Mogg.

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A majority of Conservative lawmakers voted against Brexit in the 2016 referendum, but many have since switched while up to 80 of the 316 Conservative lawmakers now support a sharper split with the EU than May is proposing.

- NO DEAL

Both London and Brussels say they want a divorce deal, though there is limited time if the British and EU parliaments are to ratify a deal by March 29.

Two documents must be agreed: the Withdrawal Agreement Treaty and a declaration on the framework for a future relationship.

Agreeing an arrangement for the Northern Irish border with the Republic of Ireland is a hurdle, though diplomats said a deal could be clinched at the very last minute.

If May cannot get an overall deal in October or November, an agreement could be reached at the Dec. 13-14 EU Council.

- DEAL REJECTED

Any deal must be approved by British lawmakers. If they reject it, Britain would face leaving the EU without an agreement. The country would move from seamless trade with the EU to customs arrangements set by the World Trade Organization for external states.

Many business chiefs and investors say a “no-deal” Brexit would weaken the West, panic financial markets and block the arteries of trade. Brexit supporters say such fears are exaggerated and Britain would thrive in the long term outside the EU.

May is betting that fear of a “no-deal” outcome will push many Conservative and Labour lawmakers to support a deal.

Parliament will have votes on the Brexit deal and on the Withdrawal Agreement and Implementation Bill. In recent votes May has had a majority of around six on major Brexit issues.

In a no-deal scenario, other options include seeking an extension of the Brexit negotiations or parliament calling for a rerun of the referendum.

2) LAST MINUTE DEAL

British politicians are trying to persuade German Chancellor Angela Merkel and French President Emmanuel Macron to ensure the EU accepts a deal that May can sell to her parliament.

Around 85-90 percent of the Withdrawal Agreement text is settled, according to Cabinet Office minister David Lidington.

In that case, little would change immediately after Brexit day because a transition period would last until Dec. 31, 2020.

May has said she will fight the next UK election, due in 2022. However, she would probably face a challenge within her party soon after Brexit as few Conservative lawmakers think she can win a national election.

Business leaders fear politicians have given little thought to how the UK should operate in practice after it leaves the EU.

3) BREXIT REVERSED

If the UK slides into chaos, there is a chance Brexit could be stopped through a popular vote, though May rules out another Brexit referendum. Opinion polls show Britons remain divided, though some have recently signaled a swing toward support for staying in the EU.

A YouGov poll, conducted July 31-Aug. 7 for the pro-referendum “People’s Vote” campaign, found 45 percent supported a new referendum whatever the outcome of talks with the EU, while 34 percent opposed it.

Calling a rerun of the referendum on what was a Conservative brainchild would sink the premiership of any leader of the party. Labour’s Corbyn has indicated he does not support another referendum but has not explicitly ruled one out.

Brexit supporters say a second referendum would trigger a major constitutional crisis.