Like white smoke from the Vatican announcing a new pope, the signal from Britain’s Cabinet table says: We have a decision.

After a year and a half of negotiating with the European Union — and fighting with itself — the U.K. government on Wednesday backed a deal to allow Britain’s orderly exit from the bloc, and paint the outlines of future relations.

Prime Minister Theresa May’s fractious Conservative government agreed on a deal that solves the key outstanding issue — how to ensure a frictionless border between the U.K.’s Northern Ireland and EU member Ireland after Brexit. The “backstop” plan involves keeping the U.K. in a customs union with the EU until a permanent trade treaty is worked out.

It’s a breakthrough, but the path to Brexit day — just over four months away on March 29 — remains rocky.

Here’s a look at what is likely to happen next:

BEELINE TO BRUSSELS

May is due to update Parliament on Thursday on what has been agreed, while Brexit Secretary Dominic Raab will likely head to Brussels to meet with chief EU negotiator Michel Barnier.

Barnier declared there has been “decisive progress” toward a deal — the phrase that allows EU leaders to call a special summit to approve the deal. They have penciled in a meeting for Nov. 25.

The deal consists of two parts: a legally binding withdrawal agreement — which includes the border backstop — and a looser framework for future relations. The two sides have given themselves a transition period until the end of 2020 to work out the details of future trade ties.

PERIL IN PARLIAMENT

Once the EU has signed off on it, the deal also must be approved by the European and British parliaments

May hopes to get it passed by U.K. lawmakers before Christmas. Business groups warn that most U.K. companies will implement Brexit contingency plans — cutting jobs, stockpiling goods, relocating production — if there isn’t clarity by then about the terms of Brexit.

But she faces an uphill battle. May’s Conservative Party doesn’t hold a majority of seats in the House of Commons, and relies on 10 lawmakers from Northern Ireland’s Democratic Unionist Party to win votes. But the DUP says it will reject any deal that treats Northern Ireland differently to the rest of the U.K.

Several dozen pro-Brexit Conservatives have vowed to oppose any arrangement that keeps Britain in a customs union, and tied to EU trade rules, indefinitely.

The main opposition Labour Party also says it will oppose any deal that doesn’t offer the same benefits Britain currently has as a member of the EU’s single market and customs union.

May is calculating that, faced with the prospect of a chaotic “no-deal” exit — complete with financial turmoil, gridlock at U.K. ports and shortages of essential goods — most Conservatives and some opposition lawmakers will crumble and support the deal.

UNCHARTED TERRITORY

If Parliament rejects the deal, Britain enters unknown territory.

Lawmakers could try to send the government back to the negotiating table with the EU, though there’s no simple mechanism to make that happen. They could defeat the government in a no-confidence vote in an attempt to trigger a national election.

Lawmakers could even vote for a new referendum on EU membership, though it seems unlikely there would be time to hold one before the U.K.’s scheduled departure date. The U.K. will cease to be an EU member on March 29 — deal or no deal.

Iain Begg, a professor at the London School of Economics’ European Institute, said rejection of a deal would trigger a major political crisis because Britain’s patchwork constitution offers no “prescribed way out of that dilemma.”

He said in that case, “we really are into a period of great uncertainty about what happens next. I think nobody can know how it would unfold.”

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