The divorce negotiations may go to the wire.

The negotiations over the British withdrawal from the European Union were supposed to be over by now. But the October European summit came and went without a deal. And a much-hyped challenge to Prime Minister Theresa May’s leadership fizzled out Wednesday, in part thanks to the reaction to the gruesome off-the-record language from critics in her party.

The Brexit process remains a multilevel negotiation, where actors send out signals and seek to frame the discussions to rally support, obfuscate and intimidate. With just over 150 days to go until Britain is due to leave the European Union, here are five things to watch:

1. Can Theresa May deal with Tory MPs?

Divisions over Europe in Britain’s Conservative Party stretch back decades. May has successfully papered over the cracks since becoming leader, but at some point, the prime minister will have to finalize the details. And whatever deal she strikes will disappoint some Conservatives.

The government is trying to persuade Conservative “Remainers” that the alternative “no deal” exit is far too costly for Britain. And they are communicating to members of the pro-Brexit European Research Group (ERG) that voting down the deal might create the conditions for another referendum, which might lead to Brexit not happening at all. And, of course, the government is holding out the dire prospect that defeat for a Brexit vote in the House of Commons might herald a new election — and a Labour government headed by Jeremy Corbyn.

Will May’s tactics work? For some Conservative MPs, the Brexit issue matters more than party unity, whatever threats are leveled. Pro-remain MPs such as Anna Soubry and Ken Clarke are likely to attempt to bring about another referendum. The ERG contains a number of MPs who see any concession to Brussels as a betrayal of the 2016 referendum.

Despite this opposition within the Tory side, it is far from clear there is a sufficient or unified pull to depose the prime minister. But its refusal to support the government causes problems in Parliament and may yet lead to a defeat over Brexit.

2The parliamentary math gets tricky

Any Brexit deal requires the support of Parliament, but the Conservatives do not have a majority in the House of Commons — even if every Tory backed Theresa May. How Northern Ireland is treated in the final withdrawal agreement will matter greatly — can May rely on the critical support of the Democratic Unionist Party?

And the Labour Party has its own divisions — some MPs will back the government’s leave plan. Some are pro-remain but argue that an acceptable deal would be better than the prospect of a no-deal outcome. Others still will vote against any deal, hoping to secure another referendum.

Calculating the numbers is devilishly difficult, with many MPs publicly undecided on how they intend to vote — many, of course, want to see whatever deal materializes before they decide. And there is another complication. Some Labour MPs might feel constrained from supporting the Brexit deal by a fear of rebellion in their own constituencies. The recent Labour Party conference passed a change to party rules, making it easier to challenge a sitting MP. Those seen to be supporting a Tory government over Brexit might find themselves early test cases of the new procedures.

3. Public opinion shows profound divisions

Yes, 700,000 pro-remainers took to the streets of London this month to demand a “people’s vote” on any Brexit deal. Yet public opinion remains largely stable and profoundly divided over Brexit.

Recent data suggest a slight shift toward remain. However, this shift seems to be made up mainly of people who either did not or could not vote in 2016, now stating that they would vote in this way, rather than leavers changing their minds.

It’s also far from obvious how such a vote would come about. In the event that Parliament could not agree on a Brexit deal, it is conceivable that MPs might opt to delegate the decision to the public. But this would require an extension to the Article 50 process, and it’s not clear Parliament could agree on the form of question to be asked.

4. Ireland’s border is a huge question

The Irish border has become the most intractable issue in the withdrawal negotiations, as Northern Ireland is part of Britain, but the Republic of Ireland is, and will remain, an E.U. member. Whatever Brexit deal is struck (or not) will have a significant impact on trade and security. However, for the Democratic Unionists, a Northern Ireland party whose votes give May a majority in Parliament, it is also integral to questions of identity and their place in Britain.

The remaining E.U. member states have been solidly behind the Irish government, refusing to countenance signing off a withdrawal agreement unless it contains an Irish “backstop” that would keep Northern Ireland in the customs union and parts of the single market to avoid an internal Irish border even in the event of a “hard Brexit.” There is still some hope in London that Dublin might agree to a slight softening of the language around the backstop, if only because the Republic of Ireland would be the member state worst affected by a no-deal outcome. As of yet, however, there seems little sign of this happening.

5. And the E.U. has other worries

Brexit is not the only or even the top priority for the E.U. Concerns over migration and the continuing demands of euro-zone governance tend to take priority. The other 27 E.U. states have been happy to entrust the process to their chief negotiator, Michel Barnier, thereby ensuring continued unity. And, of course, member states also have been keen to benchmark Brexit as an unfavorable outcome for any state considering following suit.

However, the actual prospect of Brexit may start to sharpen minds. A punitive Brexit could have long-term political and economic consequences not just for relations between the E.U. and Britain but also the wider geopolitical and security landscape in Europe. If the British people felt they were being punished by the E.U., support not only for European integration, but conceivably also for solidarity within NATO, might weaken.

European negotiations have a habit of going to the wire — and Brexit will be no different. But with Brexit, there is a legally defined end date — March 29, 2019 — and the default outcome is not the status quo ante but a no-deal scenario that would be profoundly damaging. The stakes, then, could not be higher.

Tim Haughton is associate professor of European politics at the University of Birmingham. Anand Menon is professor of European politics and foreign affairs at King’s College London and the director of UK in a Changing Europe.