Here’s what to know about the latest Brexit vote

British Prime Minister Theresa May will try again Tuesday to get a Brexit deal through Parliament, with 17 days to go before the March 29 deadline.

May promised late last month that she would give the UK Parliament a chance to vote again on a Brexit deal after going back to the European Union to try to negotiate changes that could win the backing of members of Parliament (MPs).

The focus of those negotiations has been the “Irish backstop,” an aspect of the deal that guarantees no hard border between Northern Ireland and the Republic of Ireland after the UK splits from the EU.

Late Monday night, May and European Commission President Jean-Claude Juncker announced some last-minute additions to the Brexit deal, including legal assurances that the backstop would be temporary.

But will it be enough to get a Brexit deal through Parliament this time?

Parliament defeated May’s Brexit deal in January by a stunning 230 votes. The prime minister may need to offer something different to have a chance of success this time around.

Whether these legally binding assurances about the backstop will be enough to get the deal through Parliament is the question dominating the debate ahead of Tuesday’s vote. In the meantime, here’s what you need to know before the vote, which is expected around 7 pm London time.

The EU-UK agreed on legal guarantees to the backstop. Will it be enough?

The Brexit deal combines a 585-page agreement with a short political declaration on the future EU-UK relationship. But what’s holding everything up is the issue of the Irish backstop.

The backstop is basically an insurance policy that says if the EU and UK can’t define their future partnership after Brexit, there will be no physical checkpoints or controls on the border between Northern Ireland (part of the UK and soon to be an ex-EU member) and the Republic of Ireland, an independent country that’s also an EU member state.

To achieve that, the entire UK will stay in a customs arrangement with the EU, and Northern Ireland will more closely follow the EU’s regulations. The backstop ends when both sides agree to a permanent arrangement that keeps the border open and the UK can’t pull out of it unilaterally. (Here’s an explainer on why that’s important.)

Brexiteers — those who want to a hard break with the EU — loathe this plan because it keeps the UK and EU closely aligned, which they see as trapping the UK in an indefinite relationship with the bloc.

The UK has sought “alternative arrangements” to the backstop but have failed to find any that would satisfy the EU or truly prevent a hard border. And the EU has stayed firm on its stance that it won’t reopen the text of the withdrawal agreement.

Late Monday night, the EU and UK reached a breakthrough of sorts.

May and Juncker said they’d agreed on legally binding guarantees — basically add-ons to the Brexit deal — that the backstop is intended to be a temporary arrangement.

There were three components to these guarantees. The first gave legal force to a letter in January between EU leaders, which basically said that the backstop is an insurance policy to be used if, and only if, no other option exists to keep the Irish border open. It also stated that the backstop won’t be the default permanent solution to the future EU-UK relationship.

The second reiterates that both sides will start negotiating new trade arrangements immediately and seek to find a solution to the backstop by the end of the transition period in 2020.

And the third component involved a unilateral UK statement that said it could seek to get out of the backstop if it felt the EU wasn’t negotiating in good faith. This was more of a guarantee that May gave to herself, but the EU didn’t openly object.

These addendums to the withdrawal agreement would all empower the UK to seek recourse from independent arbiters if it felt the EU wasn’t negotiating in good faith as they tried to figure out their future relationship and protect the Irish border.

But as soon as May tried to sell these additions as major “legal changes” to the backstop, UK Attorney General Geoffrey Cox quickly spoiled the celebration.

Cox’s legal advice, published before the vote on Tuesday, said that the core of the backstop remained “unchanged.” The new assurances lessened the risk that the UK would be stuck in the backstop indefinitely, he concluded, but since the actual Brexit deal didn’t change, the UK remained bound by its original terms.

The legal commitment — which the EU had floated Friday — may bring over some converts because “that provides more assurances on the good-faith enterprises of the European Union than it does in the withdrawal agreement,” Anand Menon, the director of UK in a Changing Europe, told me last week.

But it’s unclear, especially with Cox’s legal advice, if this will be enough to get May’s deal through a second time.

Parliament will vote on May’s deal on Tuesday. Then, who knows.

May’s Brexit deal when the UK votes on Tuesday ultimately looks very similar to the one Parliament rejected in January; there are just those few extra guarantees. Which means May may face another embarrassing defeat in Parliament once again.

But it is March, with less than three weeks to go until the Brexit deadline. The calendar alone may convince members of Parliament to vote for a deal, especially if they fear the possibility of a no-deal Brexit and its catastrophic consequences.

May has also been trying to woo members of the Labour opposition party who are pro-Leave with funding for their constituencies. And she’s tried to make the “Hotel California” pitch to MPs — especially hardline Brexiteers — that if they don’t vote for her deal now and break up with the EU on March 29, the UK might never leave.

That might be a bit dramatic. But there is a much greater chance that Brexit could be delayed.

May has promised members of Parliament two additional votes if her deal fails on Tuesday. She’s said they would happen in succession, on Wednesday and Thursday.

On Wednesday, Parliament would vote on whether it wants to leave the EU without a deal on March 29. The deeply divided Parliament can’t agree on much, but it has agreed in the past that it wants to leave the EU with an agreement in place, so no-deal seems likely to get defeated.

If the no-deal measure went down, then on Thursday, Parliament would vote on whether to seek a limited extension to Article 50, the provision of the EU treaty under which the UK is withdrawing from the bloc. May has indicated this would be a short-term extension, which would simply postpone Brexit for a few months. This wouldn’t eliminate a no-deal scenario. That scenario just wouldn’t happen on March 29.

And any extension, of any length, will require approval from the EU member states.

“If the UK asks for an extension, it will be a short extension; everything suggests that,” Michael Leigh, a fellow at the German Marshall Fund and former EU commissioner, told me last week.

That’s likely to mean two months. European parliamentary elections take place May 23 to 26, and Juncker has indicated that the UK must leave the bloc before that date or it is bound to participate in those elections.

In the past, EU leaders had been reluctant to grant the UK an extension unless a legitimate reason existed — something that could fundamentally change the Brexit outcome, such as another referendum vote on whether to leave the EU or new general elections. And now, even if May’s deal does pass on Tuesday, the UK may need to request a short technical extension because it needs to pass the Brexit deal into domestic legislation, which probably can’t happen in two weeks.

Moving the deadline so the UK could continue arguing didn’t seem likely before, but the EU also wants to avoid the chaos of a no-deal scenario, which would still be bad for the EU (if much worse for the UK). The EU likely doesn’t want to take the blame for that fallout, especially if it’s within its power to avoid by just pushing back the deadline. Still, all 27 EU member states would have to unanimously approve the extension.

The EU would likely make this decision at the European Council summit starting March 21, on the brink of the Brexit deadline.

If the EU rejects a Brexit extension, anything could happen next: a no-deal Brexit, or even a third vote on the Brexit deal, though Juncker also said on Tuesday there would be no third chance.

If a third vote could happen, a lot would depend on how badly May’s deal is defeated — if it is defeated — on Tuesday. This isn’t likely to be a 230-vote beating like last time. If it’s a close vote — say, 10 votes or so — it’s possible May would make a third attempt.

But if it’s much more than that, even 50 or 60 votes, Menon said, “I’m not sure we’re going to go to a ‘meaningful vote three.’”