Should the SNP promise another independence referendum in their next manifesto?

To promise or not to promise?

That is the question Nicola Sturgeon has to answer before next year’s Scottish Parliament elections.

There are clear risks to promising a second independence referendum.

Some of those who voted No in last year’s referendum but backed the SNP earlier this month might not vote for the party again if they think a vote for the SNP is a vote for independence.

Today’s poll suggests that may be a risk the First Minister can afford to take.

Only 7% of those who voted SNP in the UK election say they’d be less likely to vote for the party if it did promise a referendum.

But there is little point in the SNP promising a referendum if it looks likely to be lost.

A second defeat would certainly mean the issue was off the agenda for a generation at least.

And today’s poll shows that, despite the SNP’s General Election landslide, there is still a majority, albeit a small one, in favour of remaining part of the UK.

The SNP might feel it could turn so small a gap around, but winning referendums on major constitutional change is difficult.

The nationalist movement probably needs to have 60% support in the polls before it could be sure of winning.

But not to promise a referendum could be risky, too.

The support and enthusiasm the SNP now enjoy might dissipate if an independence vote is taken off the table.

Meanwhile, there is that other referendum, on Europe.

Scotland is keener than the rest of the UK on staying in Europe. In the event of a narrow UK-wide vote to get out, it could find itself on the losing side.

Such an eventuality would apparently persuade most Scots there should be another referendum.

But will Nicola Sturgeon want to rely on David Cameron failing?

Report John Curtice, Professor of Politics at Strathclyde University.

What our poll found.

Poll May 2015 | Create infographics