By Therese Raphael

As negotiators from the UK and the EU meet in Brussels this week, Brexit is said to be entering its endgame.

This isn’t an ordinary endgame though: All the major pieces are still on the board and pretty much the full range of potential outcomes — from no deal to no Brexit, and everything in between — remain live possibilities. Mapping the potential outcomes isn’t easy.

Since the two-year countdown to Brexit ends on March 29 and any deal requires UK and EU parliamentary approvals, the window for a bargain effectively closes in the next few months.

Either Britain will leave the EU with a negotiated agreement or it will exit with no deal at all, upending a vast array of trading relationships and complicating future negotiations with the EU and other countries.

A new paper from the UK’s Institute for Government helpfully lays out five scenarios that could unfold this autumn.

The upshot is that “the risks of either a deliberate or an accidental no deal are quite high, given the apparent stalemate in the negotiations, the precariousness of the prime minister’s parliamentary position and the defaults now incorporated in the system.”

Of the five scenarios, only one envisions a relatively smooth route to an orderly Brexit: It posits a successfully negotiated withdrawal agreement and parliamentary approval. The other four carry a very high risk of a no-deal Brexit.

UK Prime Minister Theresa May could, for example, strike a deal that the UK parliament then rejects on the grounds that it leaves Britain a “vassal state,” as Brexiteer Jacob Rees-Mogg put it.

Ms May could try to renegotiate, of course. But she might run out of time or get turned back by Brussels.

Although the bias in the UK parliament is clearly to have a deal, there’s no agreement on what kind. And even if parliament did manage to nudge the government back to the negotiating table, it’s not clear that it would get an approvable option back.

What makes this particularly devilish is that the old Leave versus Remain division has effectively become a deal or no-deal division. There are many Leavers who don’t like Ms May’s proposed deal, but who would still favour an agreement of some kind because they think parliament might reject a no-deal result, throwing Brexit itself into doubt.

Then there are Remainers who don’t like Ms May’s proposal but who would support it as preferable to the cost and chaos of no deal at all.

Against that possible coalition of the disgruntled-but-willing is a potentially stronger force: Remainers who oppose Ms May’s deal because they find it too great a compromise and hope that they can cancel Brexit altogether; and Leavers like Rees-Mogg who oppose it as a sell-out.

If that isn’t confusing enough, party affiliation is no guide here. There are Labour Party MPs whose main priority is ensuring Britain doesn’t leave without a deal; and others whose chief interest is in overthrowing the government, whatever happens with Brexit. While the prime minister has won key votes with the help of some Labour Leavers, it’s unclear if she’ll be able to count on them.

It’s the same, pretty much, on the Tory side: There are those who want to get over the line on Brexit with a deal of some sort, those who see Ms May’s proposed deal as an economy-killer, and others for whom only a total break with all EU structures is acceptable and who believe Ms May must be relieved of her position in the process.

The Conservative Party conference in September is likely to be a beauty parade of would-be prime ministers touting their alternative Brexit visions.

And yet even these scenarios don’t account for the full range of possibilities. Say Ms May gets an agreement. The UK parliament must pass a motion to endorse it and then must pass the Withdrawal Agreement Bill for it to go into effect. But disgruntled members could at any point seek to wreck the deal.

Not enough scenarios? If the UK parliament rejects the deal, the government could seek to extend the Article 50 deadline, which requires unanimous EU approval, to allow more time to renegotiate. While unlikely, MPs could also try to force the UK government to call a second referendum.

And then there’s EU approval: The European Council needs to obtain the European Parliament’s approval by a simple majority before it can conclude the withdrawal agreement.

Expect a frenzy of activity from both deal and no-deal camps. Nigel Farage, the former leader of the UK Independence Party, has announced a grassroots tour to oppose Ms May’s Brexit plan. Another hardliner, Arron Banks, is encouraging Brexiteers to join the Tories in the hope of bouncing Ms May into a hardline Brexit or replacing her. On the other side, there will likely be more anti-Brexit protests and pleas from businesses to minimise the pain.

A Brexit soft landing, it seems, is as much a question of luck as negotiating skill at this point.

- Bloomberg