Resignation would appear to be flavour of the week in Scottish politics. Five days after Wendy Alexander fled from the top job in Scottish Labour, Nicol Stephen decided he had had enough of leading the Scottish Liberal Democrats. Resignation is always hazardous for politicians, especially those who lead their party. The very act of saying, “I'm quitting” invites inquiry as to an ulterior motive. So it proved on Wednesday night, when Mr Stephen was at first not fully believed by journalists.

The strength of feeling in his personal statement, when he spoke almost bitterly about the impact politics has on family life, was enough, though, to quell the speculation.

Mr Stephen, it has to be said, could not be described as a dynamic leader. His approach to the job appeared ultra-cautious, sometimes to the point of anonymity.

Now, with his sudden resignation, he appears to have thrown that caution to the winds, although, in truth, friends say that he has been questioning his political role for the past year.

There can be no doubt that he found the shock of not being in coalition government unnerving - so much so that in the immediate aftermath of last year's election his profile became almost subterranean. Tavish Scott, his friend and colleague, took on much of the burden of trying to keep the party, with only 16 MSPs out of 129, in the public eye.

That period passed and soon he began to look as though he was, at least, relishing the weekly joust at First Minister's Questions with Alex Salmond. A fine antipathy between the two helped, of course. Mr Stephen was never predictable in his questions, sometimes leaving the First Minister very much on the back foot.

The high point of his leadership was when he led his party to an astonishing victory over Labour in the Dunfermline and Fife East by-election. Many in his party talk glowingly still of the drive he brought to that campaign. A pity he did not show that side of himself more often.

If there was a big downside to Mr Stephen's time as leader, it was that the party never found an issue to identify with. Under Jim Wallace, the Lib Dems were for abolishing upfront student tuition fees and free personal care of the elderly, and they got their reward from Scottish voters in 2003. However, by 2007, answering the question “What are the Scottish Lib Dems for?” became a poser too far and the answer “Forming coalitions with Labour” did not seem adequate. Mr Stephen, certainly, never quite found the answer.

A minority party has to carve out a niche for itself, especially in opposition. It also has to appeal to voters with its own idiosyncratic platform over the hubbub of the main parties.

How to do that will be the main concern of the next leader, who will, unless this unpredictable party altogether loses its grasp on reality, surely be the affable and user-friendly Tavish Scott. If he does get the job, and can find a unique selling point for the Lib Dems, the party can perhaps think again of breaking out of its Highland and Borders redoubts. It is, though, perhaps just as well that Mr Scott is said to like a challenge.

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