Where can the Yes campaign look now for the momentum to carry it to possible victory in next month's independence referendum?

The televised debate between the SNP First Minister Alex Salmond and Better Together leader Alistair Darling was an opportunity to change the script.

Many people expected Mr Salmond to win the debate and Yes supporters were hoping for a boost to narrow the lead for No in the polls.

It did not turn out that way and most commentators called the night for Mr Darling, as did the snap ICM poll published in the immediate aftermath.

Both sides have since claimed victory and it is true that the same poll showed undecided voters had scored the contest quite differently. A clear majority of "don't knows" said they were convinced by Mr Salmond. Yet he does not appear to have done enough for a decisive shift. What more can he and the Yes campaign do in the coming weeks to change this?

Mr Salmond's performance in this first head-to-head TV debate was strangely muted and misfired. Both this and the approach from Alistair Darling were a surprise, with the former Chancellor giving the kind of aggressive and passionate performance many expected from Mr Salmond.

Mr Darling put his legal background to good use, homing in on key questions about the Scottish economy and forcing Mr Salmond onto the back foot. The First Minister attempted the same tactic, repeatedly challenging his opponent to state whether he agreed with the Prime Minister that an independent Scotland could be successful. But his other targets were ill-chosen and Mr Salmond failed to press home the point about the Prime Minister's remark.

The SNP leader's biggest failure in the debate was his inability go put across his vision of an independent Scotland. He is usually strong on the opportunity offered by self determination to deliver a fairer, more progressive and prosperous Scotland.

He seemed too often on the defensive. Many of his supporters will have been longing for him to go on the attack about the alternative futures for Scotland.

Because Mr Darling managed to focus on questions Mr Salmond could not or did not answer, he was able to avoid facing too many himself. He did not need to lay out a positive future for Scotland within the Union.

It became plain during the debate that the currency issue is a major issue for the Yes campaign. Mr Salmond may well be right that a currency union is likely, even almost certain if there is a Yes vote, despite disavowals from his Unionist opponents. But insisting it will happen is not enough. It seems all the more important to have an answer in regard to a Plan B.

The Yes campaign is, of course, much more than just Mr Salmond; a message members of the Radical Independence Campaign took to thousands of doorsteps in a mass canvas yesterday. But, at this stage, the Yes campaign would have hoped for a groundswell backing change, led from the top.

If Mr Salmond is to lead Scotland to independence, he needs to find some fresh momentum, and very soon.