Rishi Sunak has won praise after chasing the hard yards to get the EU to redraw the controversial Northern Ireland protocol. Now, he has to convince his party to fall behind it.

It may well be an opportunity he relishes, given that so far, the noises coming from Tory MPs about the “Windsor Framework” agreed with European Commission president Ursula von der Leyen seem to be broadly positive.

However, the road ahead is not entirely hurdle-free.

The prime minister will be looking to secure the approval of arguably one of the most important voices in the Brexit debate — Northern Ireland’s Democratic Unionist Party (DUP), which remains concerned about aspects of the deal.

The DUP has close ties with the Brexiteers of the Tory backbench European Research Group (ERG), some of whom are waiting for their judgment before casting their own verdict.

Here, HuffPost UK explains what the DUP’s position on the deal is and why it matters.

What Is The Windsor Framework?

It is a new deal struck by Rishi Sunak and the EU that will replace the Northern Ireland protocol.

At the heart of the arrangement is the idea of green lanes and red lanes. British goods staying in NI will use the green lane at ports, meaning they face minimal paperwork.

Goods travelling into Ireland will use the red lane, meaning they face customs processes and other checks at Northern Ireland ports.

A key part of the deal is an emergency “Stormont brake” on changes to EU goods rules that can be pulled by the NI Assembly.

The DUP has repeatedly said it will take time to consider the substance of the deal before deciding whether to back it.

That process could take weeks, or even months, the party has warned.

However, there is an incentive to come to a conclusion quickly.

The DUP is a joint partner with Sinn Fein in Stormont’s power-sharing execruive that is crucial to the functioning of the Northern Ireland Assembly.

Since February last year, the DUP has boycotted the assembly in protest at the previous Northern Ireland protocol, which Sunak has now replaced to address concerns around sovereignty, disrupted trade and the application of EU law.

Without the DUP’s participation, Stormont cannot function and people in Northern Ireland have effectively been left without a government.

While Sunak has said the DUP should be given “time and space” to consider the agreement, he made it clear that restoring Stormont was of vital importance.

Sunak told an audience in Northern Ireland earlier this week: “The framework is a fantastic agreement that delivers on all the things people care about. So now I hope that they do see it and see that and they can find a way to come back together.”

“It’s what you deserve.”

The so-called “Stormont brake” has been hailed as the “rabbit in the hat” in the Windsor Framework.

With it, the UK says the Northern Ireland Assembly will effectively be allowed to “block” new EU laws from applying in the country without cross-community support — a key demand of unionists.

Sunak lauded the brake as an “incredibly powerful” mechanism that would allow the people of Northern Ireland to have “control of their own destiny”.

If Assembly members, called MLAs, dislike changes to EU goods laws then 30 of them can sign a petition to trigger a vote to stop the rules from taking effect.

If the vote passes with a majority of nationalist and unionists, the brake will be pulled and the UK government will have the power to veto any new or amended EU law.

But there are some concerns about potential discrepancies in how the UK and EU interpret the brake, after the EU described it as an “emergency mechanism” that could be used “in the most exceptional circumstances, as a last resort”.

Sammy Wilson, the DUP’s chief whip, told Times Radio that the Stormont brake “is not really a brake at all” and that it was just a “delaying mechanism”.

He said the UK government would have the final say over whether to veto a law, which he said it would be reluctant to do due to being “fearful of the consequences of trade for the rest of the United Kingdom”.

“The price of that would be that the EU would take retaliatory action,” he said, adding that he suspects the Stormont brake would therefore be “fairly ineffective”.

According to the Times, division is emerging between the DUPs’ members in Stormont — who are keen to get the assembly back up and running — and the party’s MPs in Westminster, who are taking a harder and more sceptical line against the deal.

Although he said that changes may need to be made to the deal and that “key issues of concern remain”, the DUP’s leader, Jeffrey Donaldson did also hail the “significant progress” that Sunak had achieved.

But other key players have spoken out against the deal, with Ian Paisley Junior saying it did not “cut the mustard” and was likely to be rejected.

The DUP will also be conscious of the threat it faces from Jim Allister, the founder and leader of Traditional Unionist Voice in the lead up to the local elections in May.

Allister, a former member of the DUP, will be looking to brand any talk of compromise as a sell out and a betrayal.

What has the ERG said?

Mark Francois, the chairman of ERG, said the group’s “star chamber” of lawyers were now poring over the deal and that it would aim to come to a conclusion “within a fortnight”.

He said he had sought assurances that he “won’t find any nasty surprises” when analysing the deal.

Technically Sunak does not need the support of the DUP, or even the ERG, to get the deal through the Commons after Labour confirmed it would vote with the government.

However, the prime minister will want to get the DUP on board as that will reduce any potential Tory rebellion. If he does not, the party could use its powerful voice to undermine the deal at every opportunity — something he will want to avoid at all costs.