Will Brexit Drive Scotland out of the United Kingdom?

This article first appeared on the Council on Foreign Relations site.

The decision by British voters last June to leave the European Union has thrown that bloc into turmoil. But its implications for Great Britain could be even more profound, portending the dissolution of the United Kingdom.

Prime Minister Theresa May could trigger Article 50 of the Lisbon Treaty as early as March 15, starting the two-year timetable for negotiating the terms of the U.K.'s divorce from the E.U.

The prime minister should beware the Ides of March: It seems all but inevitable that Scotland's government will respond by calling for a second referendum on Scottish independence. The ultimate result could be the reemergence of a sovereign Scotland, more than 300 years after the Acts of Union (1706–1707) united the cross of St. Andrew and the cross of St. George.

When Scots rejected independence by a 55 to 45 percent margin in a September 2014 referendum, most assumed the matter had been put to bed for at least a generation.

The shocking Brexit vote upended that expectation. As Scotland's sovereigntist-minded first minister, Nicola Sturgeon, observes, Scots who voted for "union" less than three years ago assumed that the (still) United Kingdom would remain in the EU. And in the more recent "Brexit" vote, they overwhelmingly (62 percent) supported the "Remain" camp. Given the dramatically altered landscape, Scots deserve the opportunity to reconsider their ties with the United Kingdom.

As Sturgeon sees it, the Brexit outcome revealed "a wider democratic deficit within the U.K., where decisions about Scotland are too often taken against the wishes of the people who live here." Her Scottish National Party (SNP) has been cheered by the comments of no less than former U.K. Prime Minister Tony Blair, who says Brexit makes the case for Scottish independence much more credible.

In October, the Scottish government published a draft bill that would (if approved by the Scottish Parliament at Holyrood) launch consultations to authorize a second referendum.

Related: Scottish Labour, Conservatives won't unite to preserve U.K.

Wittingly or not, Prime Minister May has bolstered Scotland's independence movement by insisting on a "hard exit" from the EU.

Scottish members of the U.K. Parliament in Westminster worry about losing access to the EU's single market. True, trade between the U.K. and Scotland—worth £49.8 billion ($61 billion) in 2015—is four times the value of Scottish exports to the rest of the EU. But the benefits of the single market are substantial, and many Scots are not willing to risk them in return for greater U.K. restrictions on migration.

On February 7, the Scottish Parliament voted 90-34 in favor of a motion that the European Union (Notification of Withdrawal) Bill should not proceed. Although purely symbolic, it sent a clear message that Scotland opposes a hard Brexit.

In an effort to preserve Scottish access to the continental market, Sturgeon's SNP government in December released "Scotland's Place in Europe." The paper set out "compromise proposals" designed to allow a post–Brexit Scotland to maintain as many links with the EU as possible.

The complex, and probably unworkable, scheme would require the U.K. Parliament to devolve additional powers to the Scottish Parliament—including control over immigration, business regulations and international trade negotiations, among others. But the U.K. government has still not formally responded to the SNP paper, and SNP officials have accused the May government of attempting to hide documents setting out its views.

More generally, Scottish officials are increasingly annoyed that their concerns are being ignored as the U.K. government proceeds with its Article 50 plans. Disentangling Britain from the EU will have enormous implications for the U.K.'s devolution settlement with Scotland (as well as with Wales and Northern Ireland), the London-based think tank Chatham House says.

As numerous laws and powers are repatriated from Brussels, U.K. and Scottish officials will bicker over the division of authorities on matters ranging from immigration to agriculture to trade. Sturgeon complains about the lack of consultation between London and Edinburgh. "Scotland's voice is simply not being heard or listened to within the U.K.," she says.

May is on firm legal ground in deciding to go it alone. On January 24, the U.K. Supreme Court ruled that the U.K. Parliament had to approve any Article 50 negotiations. But that same decision also declared that May was under no legal obligation to consult with Scotland on Brexit.

The political terrain is trickier, however. The court's decision angered Scottish politicians, exposed fissures in the U.K.'s constitutional structure and renewed momentum for Scottish independence.

To be sure, the outcome of any second referendum is hardly preordained. Support for independence is up several points from a month ago, but, according to a recent BMG poll for The Herald, Scots remain nearly equally divided, with a narrow majority (51 to 49 percent) favoring remaining in the U.K. Such numbers should be taken with a pinch of salt, of course. The same polling company undercounted support for Brexit by 4 points last June, wrongly forecasting a 52-48 victory for the "Remain" camp.

More substantively, the situation is fluid and volatile. Actual Brexit negotiations have yet to begin, and the harder a break that May pushes for, the more ignored and isolated Scots will feel, likely causing opinion to swing toward independence.

Alienation from Westminster and disillusionment are already riding high in Scotland. Following the failed 2014 independence referendum, Prime Minister David Cameron's government sought to win over the Scots by passing the Scotland Act of 2016. Intended as a new and improved devolution settlement, it stated that the U.K. Parliament would normally legislate certain matters only with the express agreement of elected members from Scotland.

Cameron promised that Scotland would have the "strongest devolved parliament in the world." One of the act's selling points was the argument that continued membership in the U.K. was the only way for Scotland to stay in the EU (something it might have trouble doing as an independent state).

The outcome of the Brexit vote turned that logic on its head. Scotland stayed in the U.K. but suddenly stands to lose the EU. Brexit has shown devolution to be "worthless," declares Scotland's Brexit minister, Michael Russell. It has "exposed statements" by British officials "that the U.K. government and Scotland are equal partners" to be "empty, diversionary rhetoric."

May has offered to consult Scotland (as well as Wales and Northern Ireland) on the Article 50 negotiations, but she has also made clear that the devolved administrations will play no decisive role in Brexit. Given this context, SNP officials argue, Scotland has no choice but to vote again on independence.

Many observers expect a major announcement from the emboldened Sturgeon on March 17, when the SNP holds its spring conference in Aberdeen. This could include naming a target date for the second independence referendum, which would likely be held in autumn 2018.

Here is where things could get tricky—and could spark a constitutional crisis. Under the Scotland Act of 1998, which established the devolved Scottish Parliament, the British Parliament must consent to any new Scottish referendum. Sturgeon has declared that it is "inconceivable" that the U.K. government, in the wake of Brexit, would try to block the Scots from exercising their right to self-determination.

This may be wishful thinking. On February 2, Michael Fallon, the British defense secretary, predicted that the House of Commons would veto any such a referendum. Other British officials, while avoiding the term veto, confirm that May's government intends to do just that.

Although sources are now suggesting May could agree to a referendum vote as long as it was after Brexit. Meanwhile, Conservative Scottish members of Parliament are accusing the SNP of "weaponizing" the Brexit debate, "cranking up the grievance machine" in Scotland to ensure Britain's disintegration.

But if Theresa May has plenty to worry about, so does Nicola Sturgeon. Among the many uncertainties in the Brexit/"Scexit" dance is whether an independent, sovereign Scotland would actually be welcomed into the EU—and, if so, how soon and on what terms.

Some experts argue that an independent Scotland could be fast-tracked into the EU, potentially by 2023. However, this relies on generous assumptions about the likely reactions of the bloc's member states. Some EU countries (not least Spain) may be reluctant to ratify Scotland's EU accession, for fear of emboldening their own restive regions (Catalonia and the Basque country, in this case).

Scotland also faces a £15 billion ($18 billion) budget deficit, higher than every EU member state as a percentage of gross domestic product, including Greece, which itself has caused such turmoil for the eurozone.

One thing is clear. March 2017 is shaping up to be a momentous month in the histories of the European Union, the United Kingdom and Scotland, as leaders try to strike new bargains over how political power and sovereignty should be allocated at the supranational, national and subnational levels.

Stewart M. Patrick is a senior fellow and director at the Program on International Institutions and Global Governance at the Council on Foreign Relations.