ALBA proposes to stand as a list party in order to boost pro-independence MSP numbers at Holyrood.

According to the polls, the SNP would currently be expected to win most constituencies and as a result of doing so well, would not be allocated list seats in most regions. 

It is that which creates the logic for fighting as a separate list party – if voters vote for that party on the list they might help elect a pro-independence MSP, when backing the SNP would not.

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So to boost the number of pro-independence MSPs, Alex Salmond needs either to pick up votes from SNP supporters in regions where the SNP do so well in the constituencies that they will not pick up any list seats – or he needs to win support from the constituency voters of other parties.

Though it might pick up some activists and perhaps SNP politicians, the party will have little organisation or resource, and the success or otherwise of the enterprise will rest heavily on Mr Salmond’s personal popularity.

However, Mr Salmond is not a very popular politician. According to YouGov and Opinium only 14 per cent of all voters have a favourable view of him. Among current SNP voters the figures are 16% and 18%  respectively.

This suggests Mr Salmond has a potential market of one in six of the current SNP vote. Given that the SNP currently stand at 42% of the list vote, this suggests he might hope to pick up 7% of the list vote.

Mr Salmond is currently most popular among Conservative voters, but they are unlikely to vote for him. Both polls find that 11% of Labour voters think favourably of him. With Labour currently at 18% of the list vote, that might be worth another 1-2%.

A little under 6% is usually needed to pick up a list seat. 

So if Mr Salmond can maximise his market he and a number of other candidates might get elected.  But it does assume that pretty much every Salmond admirer is willing to vote for him.

But there is a downside risk. 

If he picks up 5% or less, the party will pick up few, if any, seats. 

Yet he may still take away from the Greens the list support of SNP supporters who were minded to vote tactically for Patrick Harvie – costing them seats without picking up any himself.

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Unionists do not want the SNP to win an overall majority on their own, for then they would be able to invoke the precedent of 2011.

Although the SNP will only achieve that target by winning heavily in the constituencies, given their current standing on the polls they could well be dependent on picking up a handful of list seats in their weaker regions – most obviously the South of Scotland and the Highlands. 

Mr Salmond might thus cost the SNP an overall majority – and that may well be much more important than the total number of pro-independence MSPs.

Of course the bigger picture may be important – the “split” in the nationalist movement might put people off both the SNP and independence.

If Mr Salmond is going to appeal successfully to SNP supporters he will not be able to spend the next seven weeks simply attacking his former party.