As the EU referendum campaign gathers momentum, polls show the UK almost evenly divided on the merits of staying in and pulling out. In Scotland, however, the Remain option is clearly in the lead at this stage. This asks some intriguing questions about what will happen after June 23 as the Scottish and European issues have become so deeply entwined. Almost all the possible scenarios seem set to increase constitutional tensions.

The first scenario is that all four nations of the UK vote to withdraw; this seems unlikely. The second scenario is that England votes to come out and Scotland to stay in. English votes mean that Scotland has to leave the EU against its will. This represents the “material change of circumstances” that Scottish first minister Nicola Sturgeon has said could justify a new independence referendum.

Tempting though it would be for the nationalists, such a referendum would be a hard sell. The issues of public finance, dependency on oil and the currency are even more acute now. Sharing the pound would be even more difficult if Scotland were within the EU and the UK outside. The whole point of the independence-in-Europe strategy is that it lowers the cost of independence by guaranteeing open borders, access to markets and free movement of labour with both the UK and Europe. With Scotland in the EU and the UK out, there would be a hard border between Scotland and England.

If Scotland were obliged to leave the EU along with England, however, matters would still change. Powers would revert to the UK as a consequence of EU withdrawal, but many of these to Scotland rather than Westminster as they are not reserved. This includes large swathes of powers in relation to agriculture, fisheries, environment, justice and home affairs, higher education and social policy. Scotland could then choose whether to align its policies in these fields more with London or with Brussels, so retaining a stronger connection with Europe if not a role in European policymaking.

Beware the English nationalists

The third scenario from the referendum is that there is an overall majority to stay, caused by Scotland voting decisively in favour and England only voting by a small majority to leave. England is then held in the EU against its own wishes. Brexiters tend to be English nationalists and this will enrage an English opinion already exercised about English Votes for English laws and what they see as Scotland’s favourable financial position. England does not have the option of withdrawing from the UK but some might be tempted to achieve the same result by encouraging Scotland to leave.

The fourth scenario is that all four nations of the UK vote to remain within the EU, avoiding a constitutional crisis in the short term. In the longer term, however, the issue would continue to rankle. David Cameron’s new deal for the UK in Europe has been derided as not living up to the early promise of a radical change in the relationship with the EU.

On the other hand, the whole episode has made it clear that the UK’s wholehearted engagement with the European project is at an end. At UK level, few of those supporting Remain have questioned the drift towards a looser union. Few have supported freedom of movement as a matter of principle rather than a burdensome obligation. The UK’s exemption from the principle of “ever closer union of the peoples of Europe” may look symbolic but it does mean that UK governments will henceforth pick and choose which bits of future agreements they will accept. The opt-out will be the norm rather than the exception. The requirement put in place by the coalition government of 2010-15 that any new transfer of powers to the EU be subject to a referendum will make governments even more cautious.

The question then arises as to whether Scotland would wish to travel in the same direction. There are distinct views in Scotland about the social dimension of Europe, freedom of movement, climate change and renewable and non-renewable energy. There are distinct interests in agriculture and fisheries. Some of these concern devolved matters, where Scotland would want its voice to be heard in the councils of the EU. Others are reserved.

At present, Scotland has a say in EU policymaking through the Joint Ministerial Committee on Europe and Scottish ministers participate in the UK delegation to the Council of the European Union. It does not participate in the European Council (of heads of state and government). These arrangements give Scotland a voice but not a vote, as the final word on the UK negotiating position rests with the Her Majesty’s Government. If differences between the two governments increase, the mechanisms could come under increasing strain.

Michael Keating is funded by the Economic and Social Research Council but the views in this piece are entirely his own.

Michael Keating, Chair in Scottish Politics, University of Aberdeen

This article was originally published on The Conversation. Read the original article.