The deal between Northern Ireland's Democratic Unionist Party and the Tories to keep Theresa May in Downing Street is likely to come down to hard cash — and the DUP's "have cake and eat it" attitude to Brexit.

The party, whose leader Arlene Foster flew to London Tuesday for talks with May, campaigned for Brexit in last year's referendum and its members often portrayed as hard Brexiteers. But like the Tories, the party is split on the issue and its main goal will be to maintain essentially the same border arrangements with the Republic of Ireland to the south and the rest of the U.K.

That will have implications for the government's Brexit negotiating stance.

The Conservative leader had hoped to shore up a swift deal with the DUP in the wake of the inconclusive British general election result. At 7:30 p.m. Saturday, the Downing Street Press office announced a ‘confidence and supply’ agreement.

Four and a half hours later, the DUP issued a statement. No such arrangement had been reached.

Unlike a majority of Northern Irish voters, the DUP backed Brexit in last year’s referendum.

Instead, three days later, the parties are still at the negotiating table and the Tories are discovering that you don't spend a lifetime in Northern Ireland politics without developing flinty negotiating skills.

Few doubt that a bargain will be struck eventually. The parties share broad interests, with some exceptions. But questions remain about the shape of the deal the Northern Irish unionists want, particularly on Brexit.

'Frictionless' trade

Unlike a majority of Northern Irish voters, the DUP backed Brexit in last year’s referendum. The unionists have said that they want to ensure there is no hard border with the Republic of Ireland and that cross-border trade remains "as frictionless as possible" — something that is crucial to the economies on both sides of the border.

But the DUP also opposes any change to the unfettered movement of people between Northern Ireland and the rest of the United Kingdom. “People in Northern Ireland, for all sorts of practical reasons, want ease of access across the border. Easy movement is good for everybody,” Nelson McCausland, a former DUP minister in the power-sharing executive in Belfast, told POLITICO. “How you reconcile that with all the other considerations is key. We have to do that in a way that does not effectively create a new border at Larne or Belfast harbor.”

What this is likely to mean in practice are some exceptions for Northern Ireland in the Brexit deal.

“The DUP want to have their cake and eat it,” said Katy Hayward, lecturer in social divisions and conflict at Queen’s University, Belfast.

“Officially the DUP say they are against a special status for Northern Ireland but in effect they are looking for special arrangements, they just don’t like the term. If it was called something else, say ‘bespoke arrangements’, that might be palatable," she said.

The DUP’s position has variously been interpreted as presaging a hard or soft Brexit, but the ambiguity of the party’s stance is as much a product of internal dynamics as a broader vision for the future of Northern Ireland, or the United Kingdom. The party was founded by Ian Paisley in the 1970s on the principle of coming out of the EU but support for the Leave campaign last year was not unanimous within the party.

The Democratic Unionists only registered as a designated Leave campaigner a month before the referendum. While Arlene Foster, then Northern Irish first minister, was hoping that David Cameron would be able to negotiate a more substantial deal in Brussels ahead of the vote, Westminster MPs such as Sammy Wilson and Ian Paisley Junior were publicly calling for a Leave vote months earlier.

The DUP is likely to prioritize investment in Northern Ireland as its price for propping up May.

The DUP’s Brexit campaign in Northern Ireland was, at best, lukewarm. The DUP received over £435,000 in donations during the campaign – an unheard of sum in Northern Irish politics – but spent barely £10,000 there. The rest was spent on the British mainland. The source of these donations is still unknown due to Northern Ireland’s donor secrecy legislation.

Westminster wing

Brexit, and the subsequent need for DUP support from the Tories, has emboldened the party’s Westminster wing, which includes many of the most Euroskeptic DUP voices. For the last decade, Belfast, and the power-sharing government, has been the most important forum for the party. But with devolution suspended, perhaps indefinitely, Westminster is now where the party can exert power.

In principle at least, a deal with the Conservatives should be very doable. The two parties have been close for some time, especially after Theresa May became prime minister last July. It has also emerged that the parties nearly came to a deal in 2015. The Telegraph reported that they came close to agreeing a formal 'confidence and supply' agreement.

The DUP is likely to prioritize investment in Northern Ireland as its price for propping up May. “There is a desire within the DUP to rebalance the economy — investment in research and development, investment in the university [Queen's University Belfast]," said McCausland. “What we are talking about here is a need to create opportunities for people.”

Much coverage of the DUP in the U.K. over the weekend focused on the party’s opposition to same-sex marriage and other conservative views. But do not expect Democratic Unionists to push their social agenda in talks with the Conservatives, said Jonny Byrne, lecturer in politics at the University of Ulster. “Fundamentally this will be about economic issues."

There's also the vexed question of Northern Ireland's divided politics. McCausland says the party will want to press its case on that front too. "It would be reasonable to look for similar investment in aspects of culture that would be of the people in the unionist community,” he said, reflecting a belief among unionists that they lose out to the Nationalist community under current arrangements. He would like to see the designated days for flying the union flag from public buildings increased and a renewed focus on “the Britishness of the United Kingdom” as a well as a new deal for Northern Irish soldiers in the British army returning home after active service.

The party has learned from watching the fate of junior parties in more or less formal coalitions, said Byrne. The smaller partner is often blamed by voters for what they don't like but not given credit for what they do. "They will want flexibility in any arrangement so they can pick and choose what they are voting on at the same time as giving Theresa May stability,” he said.

While such an ad hoc approach will suit the DUP, it makes it all the harder for the Conservatives to craft a deal that will keep the government in power until the end of the Brexit negotiations — let alone until the election scheduled for 2022.