Both sides put own spin on the debate

Sources close to Mr Salmond also accused Mr Darling of conceding on his one key point in the campaign, the issue of currency union and interpreted his comments as an acceptance an independent Scotland could use sterling.

But those attached with the Better Together campaign again focused on the First Minister's position on currency union, claiming he failed to offer a coherent Plan B and that undecided voters would swing behind a No vote.

One said: "On the crucial questions, Salmond failed to deliver. As Alistair said, good lines are not necessarily good answers."

Special advisers to Alex Salmond and Scottish labour leader Johann Lamont, as well as Chief Secretary to the Treasury Danny Alexander, Scottish Health Minister Alex Neil and leading backroom Tories, watched the debate from behind the assembled press.

One leading official in the Scottish Government told The Herald it was "clear from very early on Alex Salmond was in the ascendancy and that only grew as the debate progressed".

The official added: "There was one winner only and that was the First Minister. That may have been the decisive moment in the campaign.

"Darling made a major concession on currency, his one campaign issue. He also failed to give any clear ideas on what future powers Scotland would receive in the event of a No vote."

Mr Neil said: "The First Minister was the clear winner and the polls show that. It was very decisive. The difference was between a vision of the future for an independent Scotland, which Alex gave, and the negativity and No that came from Darling.

"As we head into the last three weeks and into the final straits the dividing lines are becoming much clearer,"

But Mr Alexander said: "Alistair did win because he was asking the questions the undecideds want answered. Before Alex Salmond started shouting everyone down he was unable to give any answers on currency.

"He couldn't give any answers on how Scotland would fill its black hole and then said he had three currency Plan Bs. People don't want jokes about buses, they want to know how they will be paying their fares. Alistair Darling also conveyed very well how we will get the best of both worlds in the UK."

One Better Together source said: "Despite all the shouting from Salmond what we are left with is uncertainty over currency matters and an inability to tell anyone about the type of money they would have in their pockets in an independent Scotland.

"Salmond had the chance to speak to millions and answer some straightforward questions and he failed.

"I didn't think he could be any worse than last time. His lack of any Plan B will have made up the minds of many undecideds. He was utterly evasive."

But one source close to the First Minister said: "We are delighted with that. The First Minister knocked him off the park. And everyone's thinking the same. Darling had no answer on jobs, made currency admissions and that was a much better all-round performance from Alex."

Meanwhile, about 60 students gathered in a bar at Glasgow University's Queen Margaret Union said Mr Salmond had delivered an improved performance in the second debate.

There was silence through much of the 90 minutes as they listened to the arguments put forward on the issues.

Caelum Davies, 20, a politics student from Wales, said: "I think Alex Salmond is coming across a bit better.

"He has been a bit smoother with his words and a bit quicker off the mark.

"Alistair Darling is probably not putting his argument across very well and that is helping Alex Salmond.

"Listening to the reaction there, it seems like the Yes campaign is doing better."

Evgeny Kravtsov, 22, originally from Russia but living in Glasgow, said: "I think Alex Salmond is definitely doing much better.

"He seems to be getting more of an audience response than Darling."

The software engineering student added: "I think he tends to come across as a little bit arrogant in debates, but that might lend him more power in this one."