Have the SNP just secured their full four-year term in office?

The blogosphere today is full of excited chatter about the highly unusual disappearance of the marked register from the Glenrothes by-election - an important issue, to be sure (Mike Smithson explains why here) and one that merits full investigation, but sadly it's far more likely to be a cock-up at Kirkcaldy Sheriff Court than a grand Labour conspiracy. And this development shouldn't be allowed to distract from what could well be the most important day in Scottish politics since the last Holyrood election, with the SNP securing a formal deal with the Liberal Democrats to pass the budget.

I've long felt that if the SNP were to struggle to see out their four-year term of office, the second budget would prove to be the danger point. Indeed, I recall Robin Harper being asked in the immediate aftermath of the SNP taking office how long he thought they could hold on, and he replied that the general feeling was two years. This seems logical - after two years, the opposition parties could make the case they were not acting hastily in bringing the government down. But the budget was the opportunity to do it, and that moment has now passed. Unless something unexpected crops up (always a possibility) the last remaining clear-cut chance to bring down Alex Salmond's administration will be the third budget a year from now, but will the opposition parties really be able to justify doing it just one year out from an election? I hope I'm not speaking too soon, but I feel the SNP may have just secured their full four-year term in office - a remarkable feat given their slender one-seat advantage in the Scottish Parliament.