What could happen next? Four potential scenarios
1) Scotland votes to Remain but the rest of the UK votes to Leave
This is the potential trigger for a second independence referendum.
Nicola Sturgeon has suggested this would be a “material change” in circumstances that could give her the right to raise the constitutional question again.
But she has also sounded a note of caution. The first minister wants to be sure the people of Scotland want a second independence vote – and that Yes would be likely to win – before calling one. That is the case whether we leave the EU or not.
2) England votes to Leave but Scottish votes keep the UK in the EU
If enough people in Scotland vote Remain, it could swing the vote of the entire UK.
This would create a constitutional headache for many in the Leave campaign, who are also opposed to Scottish independence.
There has been no suggestion that England would then look to separate from the rest of the UK in this scenario, but it seems likely that many Brexiteers would be extremely frustrated with this outcome.
3) The whole UK votes to Remain, but the Brexiteers want another referendum
This would be possible if, for instance, the European Parliament were to veto or water down David Cameron’s renegotiation, which is the supposed premise of this referendum.
Some EU officials have suggested this might happen – if so, there could be a “material change” in circumstance to justify another vote.
David Cameron, however, will not want to call one. The possibility of a second referendum on the EU will most likely depend on who succeeds him.
4) There is a general election in the next six months
It is no secret that the Conservative Party and government has become hopelessly fractured by this referendum.
David Cameron has already resigned as Prime Minister… Who will lead the party in the future? And what next for the Conservative party?