John Curtice: Persuading Scots they will be better off will be crucial for the Nationalists

DEFENCE and the implications for independence are going to be central to this debate. The one thing that distinguishes independence from devolution-max is that Scotland would be responsible for defence and foreign affairs under independence.

There was always going to be some issue surrounding defence procurement that was going to be hanging in the background in the 2015 period just after the referendum.

But in the longer term, UK defence spending is having to be cut back anyway. It’s important and an important source of investment for parts of Scotland, but it’s not as big as it was 30, 40 or even 50 years ago. The economy and people’s perceptions of the economic consequences are going to be crucial. There is no doubt that you aren’t going to vote in favour of independence unless you’ve got a pretty strong sense of Scottish identity, and while your British identity may not be non-existent it’s definitely the weaker of the two identities. That’s, in a sense, a necessary precondition. But there is no doubt that that isn’t a sufficient condition for people to vote for independence.

Some people believe in an independent Scotland that jobs are going to be as they are now because they look at the whole issue through rose – or saltire – tinted glasses. But a lot of other people out there will say they’ve got to be convinced about this.

The SNP’s big job is that they have to convince people that Scotland will be better off. At the moment, polling evidence doesn’t necessarily suggest that a large majority of people think that Scotland is going to be worse off, but equally it’s also clear there is only a minority of people who are convinced that it will be better off.

There are lots of people in the middle who are not terribly sure and what’s also clear is that if you’re just simply in the middle and not sure, it looks as though you’re inclined to say to yourself it’s not worth the risk of backing independence.

But jobs and persuading people that Scotland is going to be better is going to be crucial for the SNP. There aren’t enough people in Scotland who say: “I am Scottish, Scotland is a nation, ergo Scotland should be independent.”

The Clyde shipyards are probably seen as one of the iconographies of Scotland and in that sense people will say this is a distinctive Scottish industry and it should be retained. The reality is that there isn’t a great deal of merchant shipping coming out of the yards anymore and they’re very heavily dependent on British defence contracts.

Small numbers of decisions can have very big consequences. The yards have very lumpy order books and you have this large number of jobs, geographically concentrated with that iconography and you can see how it concentrates minds.

• John Curtice is professor of Politics at Strathclyde University.