To lose one opposition leader might seem fortunate; to lose two could be considered positively jammy. To lose them both in under a week is probably the kind of thing that only happens to Alex Salmond, whose continuing run of good luck must be unprecedented in politics.

The resignation of the Scottish Liberal Democrats’ Nicol Stephen last Wednesday was for personal reasons, unlike that of Scottish Labour’s Wendy Alexander, four days before.

They will both be spending more time with their families but Stephen departs without the disgrace of a donations scandal hanging over him.

He can also hold his head up and say, honestly, that he acquitted himself, if not brilliantly, then better than expected in his post, particularly at first minister’s questions against Salmond. His performances were the surprise of this parliament — punchy and pertinent and often the only ones to touch a nerve.

He kept his attacks focused, and on certain issues — such as Salmond’s involvement in the Donald Trump golf course — he proved to be a relentless pursuer.

In fact, like some other high-profile quitters (the leader of the SNP, for example) Stephen seemingly has done nothing to prevent his return to front-line politics one day, perhaps when his children are older and his hours are more flexible.

None of the above could be said about Alexander, whose exit from Labour’s leadership was greeted with relief by everyone except her very closest family and friends. Not for her the comeback tour.

But the two leaders — or rather, ex-leaders — do share something in the manner of their departures: they are both victims of a resurgent nationalist party which has greatly altered the political landscape in Scotland.

The success of the SNP is the big story of the year and the disappearance of two relatively minor players will soon be but a footnote. This is what is most worrying about the latest Holyrood casualty.

It is conceivable that if Stephen had been getting somewhere with his line of attack on Salmond, he might have been tempted to tough out his domestic dilemmas. The SNP do not have a commanding majority — just one seat, remember — and when they became the party of government last May, there was much speculation over their chances of survival.

Stephen and his Lib Dems decided not to go into a coalition with the nationalists, a decision surely influenced at the time by the potential precariousness of a minority Salmond administration. Back then there existed at least the possibility of ousting the chippy separatist, maybe through a no-confidence vote and a concerted assault by the Unionist parties.

Now, though, everything looks different. The nationalists have adapted well to government while the opposition has reacted allergically to opposition. Indeed, the SNP has become so popular that if there were another election tomorrow, their lead would be unassailable, according to the most recent opinion polls.

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