In one sense, it is the commitment of Mr McConnell to nuclear power and weapons that will be crucial. By tieing Scottish Labour so forcefully to nuclear power stations and to the renewal of trident, the current First Minister is actually driving the LibDems into an alliance with the SNP. The major barrier to such an alliance was Mr Salmond's insistence upon an independence referendum, but that commitment has now been substantially weakened in favour of some kind of White Paper. The LibDems could no doubt live with that, especially if it were an SNP paper rather than an Executive paper. The Greens are already (if vaguely) pro-independence and would provide back bench support for an SNP/LibDem alliance, especially if they held the balance of power.
Look at the arithmetic. It is at least possible to envisage how Mr Salmond could construct a majority; on the other hand, it is extremely difficult to see how Mr McConnell could. The SNP have 26 seats at present, while the LibDems have 17 and the Greens 7, a total of 50. The latest polls give the SNP 44 seats, with the LibDems 18; they would only need the support of 3 Greens to command a majority. On the other hand, where could Mr McConnell look for a partner? His projected 43 seats are not enough to form a minority administration, even with the benevolent tolerance of the 18 Tories. And as a tired and defeated party leader on the down slope, who would want him to carry on? If he had remained equivocal on the nuclear issues, it might have been different - but that's past praying for. And OK the polls will vary between now and May, which might make it more or less difficult for the SNP, but even winning a few more seats would not really change Mr McConnell's position.
So it looks like First Minister Salmond, to spend as much of his time as possible, blaming Westminster for everything that goes wrong and tweaking the tail of Prime Minister Brown whenever possible.