The likely impact of Brexit on the relationship between Scotland and the rest of the UK has made all the headlines but, says Kirsty Hughes, that is just the most obvious of the constitutional difficulties posed by a vote to leave.

The EU referendum could be held as early as June – if the vote is for Brexit, a UK-wide political crisis is likely.

Recent polls for Scotland suggest almost two-thirds of the population support staying in the EU. Polls in Northern Ireland also suggest a clear majority in favour, while in Wales opinion more narrowly supports the EU. So a UK vote for Brexit could mean that England voted ‘leave’ (at the level of 53% or more against the EU), while the other three constituent parts of the UK voted ‘remain’.

Depending on turnout, a Brexit vote could be extremely close overall. If England voted 53% ‘leave’ and Scotland voted 66% ‘remain’, the UK-wide vote for Brexit could be as close as 50.7% ‘leave’ and 49.3% ‘remain’.

Whether Scotland makes a dash for a second independence referendum will be just one of several critical questions in the aftermath of such a vote.

Some on the ‘leave’ side – and other undecided Tories, notably Boris Johnson – have suggested there could be a second referendum after a ‘leave’ vote, having negotiated a much ‘better’ deal from the EU. George Osborne has ruled this out.  But in the face of a constitutional and political crisis where three parts of the UK are being overruled by England, others may raise this option. Labour would have to consider its stance rapidly – would Corbyn demand a second EU referendum, or even a rapid general election on the issue (unlikely given current polls)? Would Kezia Dugdale, and Scottish Labour, change their position on Scottish independence?

The three devolved administrations in Scotland, Wales and Northern Ireland would also need to liaise rapidly. Would they go along with such a narrow vote for Brexit? They could potentially block the repeal of EU laws that would be part of the Brexit process – creating a stalemate and deepening the constitutional crisis. They could turn to the EU for advice – Brussels would find it hard not to get dragged into the debate.

Scotland, Wales and Northern Ireland could also demand a differentiated deal – so that, while England negotiates a distant relationship with the EU, they take control of as many areas of EU policy as possible, and stay as close as possible – but still outside of the EU.

Ireland will be part of this crisis too, doubtless demanding urgent talks with London on its relations with the UK and Northern Ireland in the face of Brexit, trying to avoid a hard border between North and South – and pushing the EU for support on this.

In Scotland, the key question is whether Brexit would result in  ‘no’ voters changing their minds significantly on independence – one recent poll put support for independence at 52% in that case. The SNP will face a tricky choice whether to push for a rapid second independence referendum – and Westminster might disagree if they do.

Brexit will open up a period of political turmoil and constitutional crisis across the UK and beyond; where it will end, for now, no one knows.

Kirsty Hughes is a writer and commentator on European and international politics. She has worked at a number of leading European thinktanks and has also worked as a senior political adviser in the European Commission, for Oxfam as head of advocacy, and was CEO at Index on Censorship.

Note: The views expressed in this post are those of the author, and not of the UCL European Institute, nor of UCL.

This article first appeared on the Centre of Constitutional Change.