Scotland’s National Party is arguing for a second independence referendum after gaining seats in Britain’s general election on Thursday.

Party leader and First Minister Nicola Sturgeon believes she has a mandate and Britain’s imminent departure from the EU changes the situation from 2014, when Scots rejected independence 55 to 45 percent.

She is right on the first point, but not yet on the second.

EU or UK?

Most Scots voted to remain in the European Union in 2016, but they were outvoted by majorities in England in Wales.

It doesn’t appear to have changed minds on independence yet. No poll conducted since the EU referendum has found a majority in favor of breaking away from the United Kingdom.

That could change (PDF) once it becomes clear what Brexit means.

Britain is due to leave the EU on January 31, however, European laws and regulations will continue to apply in the UK until at least December 2020. It is during this transition period that British and European authorities must negotiate their post-Brexit relationship.

Only once that deal is done can Scots make an informed decision about whether to stay in the UK or leave in order to rejoin the EU.

Balance

Voters skeptical of Brexit will hope Boris Johnson keeps the kingdom in as close a relationship with the EU as possible.

The more the UK remains in regulatory alignment with the EU, the more access it will retain to the European market.

However, that would limit its flexibility in trade talks with other nations, which, for Brexiteers, is one of the main arguments for leaving.

The challenge for Johnson will be finding the right balance.

Best for everyone

Delaying a Scottish referendum until 2021 is in everyone’s best interest.

It’s best for the whole of UK, which cannot reasonably deny the Scots a second referendum if there is a clear clamoring for one (the 2021 Scottish election will tell), but which would also benefit from having Scotland inside the union for the duration of the post-Brexit talks to argue against a hard break.

It’s best for Scots, who would otherwise be asked to choose between two uncertainties.

And it’s best for the SNP. If the polls are correct and they would lose another referendum in 2020, they could hardly argue for a third referendum a year later. Their best chance of gaining independence is waiting until Brexit is done.