NATIONALISTS are painfully aware that if they are to win the referendum in 2014 legions of Scots who don't much care for the SNP will have to vote Yes.

The statistics are clear. Even in last year's landslide election victory only 45% of voters (on a turn-out of 50%) backed Alex Salmond's party and around one-third of those did not support independence.

So in a bid to broaden their appeal the Nationalists are running two distinct campaigns in parallel.

The SNP, which cannot avoid the question of what it would do with an independent Scotland, is wrestling with the specifics. It is making the case for trying to join an England-dominated currency union, for example, and arguing, despite growing evidence to the contrary, that an independent Scotland would automatically enter the EU on the same terms as the UK. It's fair to say it's not been plain sailing up to now.

The Yes Scotland campaign, meanwhile, is presenting a more philosophical case. The point of independence, it says, is the power to choose. If you don't like the SNP's vision of the independent Scotland it shouldn't matter. All visions are possible.

Cynics might say the deeply intertwined SNP and Yes Scotland are attempting to have their cake and eat it. But no amount of grumbling will deflect them from what is an absolutely essential twin strategy.

It's why Nicola Sturgeon this week pitched in to make the Yes Scotland case before an audience at Strathclyde University which included the organisation's chief executive, Blair Jenkins, and chairman, Dennis Canavan.

She gave a measured, thoughtful and politically astute speech, aimed squarely at persuading Labour-minded voters that independence offers the best hope of delivering social justice in Scotland. The Deputy First Minister called it a pragmatic approach to independence.

But it was pragmatic in more ways than one. In a surprise announcement she also said opposition parties would be given a say in the negotiations that would take place with the rest of the UK following a Yes vote. Mr Canavan has gone further, as The Herald reports today, urging the pro-UK parties to set out their stalls for an independent Scotland.

There is much more to this than merely a desire to sound inclusive or put the pro-UK parties on the spot. May 2016, the date of the next Holyrood election, is almost as important to Nationalist strategists as October 2014, the presumed date of the referendum. It has been billed as the "first election to an independent Scottish Parliament" but the fear is that it could become a second referendum.

Who knows how talks on Scotland's share of the UK's national debt, on the future of the armed forces, or the BBC might go? Who knows how long they might take? There's a risk that May 2016 could become a vote to ratify independence, especially if it seemed the reality did not quite live up to the vision. Far better for the Nationalists to have cross party buy-in for the negotiations.

If that sounds far-fetched it's already happened. Sort of.

The previous SNP-led council in Aberdeen narrowly won a referendum to redevelop the city's Union Terrace Gardens only for Labour to fight this year's local elections on a pledge to overturn the decision. It won and it did. It speaks volumes that central belt politicians usually oblivious to goings-on in Scotland's third biggest city followed every twist and turn of the saga.

The pro-UK parties have laughed off the Nationalists' advances. It's not their job, they say, to explain how independence might work when they believe that leaving UK would put Scotland at a disadvantage. But as long as Ms Sturgeon continues to appeal directly to their voters the pressure to engage will not go away.