Scottish politics used to be predictable: Labour was the largest party, the SNP was bitter about it, the Tories were resented for existing and the Liberal Democrats were a voice of reason. But the results of the Holyrood election and last week’s Glasgow East by-election remind us that times have changed. Political parties are having to reposition themselves and adapt to the new dynamics. It’s a dangerous game, with the future of our country at stake.

For the SNP, the plan is clear. Pick fights with London, luxuriate in Labour’s decline, and hope for a Tory government at Westminster. Salmond’s conservative Nationalists and Cameron’s nationalist Conservatives combine to threaten the future of our country. We need a political party to take them on and show them up. With Labour in terminal decline, that is the role for the Scottish Liberal Democrats. We can do that by campaigning for a Parliament with more powers, particularly on tax, so that Scotland is strengthened within the UK.

Poll after poll suggests that Scots want a more powerful Parliament, but not full independence. Politicians must look beyond short-term tactics and work to deliver the long-term constitutional changes that the Scottish people really want. The Calman Commission was intended as a forum in which parties could work together on a blueprint for a strengthened Scottish Parliament.

I am clear about the kind of settlement that Calman should reach. As a member of my party’s Steel Commission I have long advocated radical reform so that more powers – especially on tax – are devolved to Holyrood. Those powers would enable the Scottish Parliament to raise or cut spending in accordance with Scotland’s needs. Such a package may be Gordon Brown’s last chance. If he survives a bloodbath at the autumn Labour Party Conference – and it’s a big if – he should commit to a fundamental re-write of the Scotland Act. If he dithers, and everything suggests he will, Labour will be holed below the waterline before they even choose a new Scottish leader. I suspect that will prove to be Labour’s tragic fate.

Later this month I hope to be elected as the new Leader of the Scottish Liberal Democrats. If I am, you can be sure that my party will argue forcefully for these reforms as the basis of Calman’s conclusions. A blueprint for a strengthened Scottish Parliament would force Alex Salmond on to the defensive. More important than that, it would meet the public’s demand for a more mature and stable settlement at Holyrood. In this respect, and in all others, I believe that the Liberal Democrats must be the leading voice of reason in Scotland’s future.

* Tavish Scott is the Liberal Democrat MSP for Shetland, and Parliamentary Shadow Secretary for Finance & Sustainable Growth.

Editor’s note: Liberal Democrat Voice is, as with all internal party elections, remaining neutral in its editorial line, and seeking to ensure balanced coverage. All three candidates have written about why about why they wish to lead the Scottish Lib Dems: Mike Rumbles’ article was published here on 4th July; and Ross Finnie’s here on 1st August. Supporters of the candidates are encouraged to submit their views to Lib Dem Voice either as an article – find out how here – or comments; but the editor will seek to ensure fair representation for all candidates.