GAMBLING on a referendum whose outcome is unsure is a risky business. Ask David Cameron, who resigned as prime minister hours after losing the Brexit ballot last June. But Nicola Sturgeon is prepared to take her chances. On March 13th Scotland’s first minister said she would seek permission from Westminster for a second referendum on Scotland’s independence from the United Kingdom, less than three years after a plebiscite in which Scots voted by 55% to 45% to stay put.

The Conservative government’s response was swift and stinging. Theresa May denounced Ms Sturgeon for “playing politics” and creating “uncertainty and division”. But Westminster is unlikely to refuse the request. It would add to the already-damaging perception of an English-dominated government that ignores Scotland. Once again a Conservative prime minister faces the prospect of presiding over the break-up of the union. And this time it is against the backdrop of perhaps the most complex international negotiations Britain has ever undertaken, as it leaves the European Union.

Ms Sturgeon wants a referendum between autumn 2018 and spring 2019, well into the Brexit negotiations but before they are complete. Last time Scotland held such a vote, Westminster left it to Holyrood to decide when it should take place. Mrs May has indicated that this time she will insist that Scotland wait at least until the Brexit talks are finished.

Ms Sturgeon is keen to take advantage of growing support for independence. At 46%, according to a survey carried out in the second half of last year by ScotCen Social Research, it is twice as high as in 2012, when the previous campaign for independence began (see chart). Holding the poll before the divorce with the EU is finalised would allow the nationalists to paint Brexit in the worst possible light: their version of the “Project Fear” employed by Remainers during the Brexit campaign.

Even so, there are arguments for delay. Support for independence is strongest and growing fastest among the young. Waiting a few years until more are able to vote (and fewer of the elderly unionists are around) could boost the nationalists’ chances. And the adverse effects of Brexit forecast by most economists—which would make Scoxit more appealing—could take time to kick in. More worrying for Ms Sturgeon, Euroscepticism is on the rise among Scots. Two-thirds either want Britain to leave the EU or would like the EU’s powers to be reduced, up from just over half in 2014. Even among the 62% of Scots who voted to Remain last year, more than half think that Brussels’s authority should be curbed. And of those who plumped for independence in 2014, a third voted to leave the EU. Stephen Gethins, the spokesman on Europe for Ms Sturgeon’s Scottish National Party (SNP) in Westminster, describes support for the EU as being in the party’s “DNA”. But it was not always so: in the 1975 referendum, when Britons decided to stay in the European project, the SNP wanted to leave. Tying the case for independence too tightly to continuing membership of the EU is risky. And rejoining the EU might not be easy. Alfonso Dastis, the Spanish foreign minister, says that Scotland would have to “join the back of the queue” for EU membership. Spain worries that Scottish independence would embolden separatists in Catalonia. Like all EU members, it can veto applications. Perhaps partly for that reason, the SNP is said to be examining the alternative of the European Free Trade Association (EFTA), whose members include Norway and Iceland. That could allow Scotland greater access to the EU’s single market, while lessening the threat of a Spanish veto. It might also avoid annoying Scots who voted for Brexit. At home, Scottish nationalists face a divided opposition. Labour’s position on Europe and Scotland is muddled. Jeremy Corbyn, Labour’s leader in London, was slammed by colleagues in Scotland for saying it was “absolutely fine” to hold a second independence vote. The most prominent unionist is Ruth Davidson, under whose leadership the Tories became the main opposition in the Scottish Parliament last year. Conservatism is a less toxic brand than it was, but Scots still care little for the Tories. That makes Labour’s shambolic state doubly harmful, since the Conservatives’ unchallenged position in Westminster makes Britain even less appealing. “This is what the SNP dreamed of in the 1980s,” says James Mitchell of Edinburgh University.

But if the politics look favourable for Ms Sturgeon, the economics do not. Weak last time, the economic case for independence is even more feeble today. Ms Sturgeon insists that free trade between Scotland and the rest of Britain will continue, whatever the result of the independence referendum. But this would be trickier if Scotland rejoined the EU or became part of EFTA. So would be maintaining the open border with England. And regulatory standards between Scotland as an EU member and Britain might soon diverge, complicating trade between the Scots and their biggest market. Scotland sends two-thirds of its exports to the rest of Britain, compared with less than a fifth to the rest of the EU. Edinburgh-based financial firms are already covertly installing brass plates in London, which would allow them quickly to shift operations out of Scotland.

Worries over trade would pale in comparison with concerns over Scotland’s public finances. A greying population and relatively weak tax base make it hard to balance the books. In the past these structural problems were partly offset by taxes on North Sea oil. A decade ago, when oil prices were high, such taxes were equivalent to 6-7% of Scottish GDP. But in the latest financial year they accounted for less than 0.1%. Curtailed investment in the oil and gas sector has contributed to a wider slowdown. In the year to September Scotland’s GDP grew by 0.7%; the rest of the country grew by 2.4%. Scotland’s budget deficit is now nearing 10% of GDP, more than twice Britain’s.

That is not sustainable for a small country. Scotland would have to bring the budget closer towards balance. Sharply raising taxes might cause rich Scots to pack up and move south. So spending would have to be slashed. For Scots who have already endured six years of Westminster-imposed cuts, this would be a rude awakening.

Still, the economic arguments were not decisive last time, contends Michael Keating, an analyst of Scottish politics at Aberdeen University. The question was which side looked riskier. Scots did not want to take a leap in the dark voting for independence. “This time,” he says, “they’ll be offered two leaps in the dark.”