It seems to me that the SNP's suggestion of holding Labour's feet to the fire is unravelling. The most recent pledge to back Labour's plans on Income Tax implies it is the other way around. The SNP, a party with little or no commitment to social justice judging by its record at Holyrood is finding itself adopting Labour policies.
It is rather different from the "King maker" role Alex Salmond envisaged. The basic reason is that having ruled out a deal with the Tories, the SNP have nowhere else to go other than supporting Labour. All very strange.