If Labour lost the election in a Glasgow sandwich bar, history may well show the SNP won it in a converted cotton mill in Liverpool. This is not to ignore the impressive, upbeat manifesto launch, the professionalism of the campaign team or the months of hard work by thousands of activists. All these elements are crucial. But there has to be a tipping point and Alex Salmond’s performance on Question Time from Liverpool’s Contemporary Urban Centre might well be that moment.

The First Minister was a voice of clarity and morality on the show and put the three other politicians – Peter Hain, Chris Huhne and Michael Howard in the shade. His warning to the people of England that Labour, the Liberal Democrats and the Tories were all threatening their National Health Service got the most enthusiastic audience reaction of the night. It has been chosen as the programme highlight on the BBC Question Time website.

The Lockerbie question (a pre-requisite it seems when SNP politicians appear on network programmes) failed to inflict a blow – quite the opposite. The audience applause was spontaneous and enthusiastic when he condemned all the other parties for doing oil deals with Libya and selling weapons to Colonel Gaddafi.

Today's Scotland on Sunday You Gov Poll shows the SNP three points ahead of Labour in the constituency and two points ahead on the list. Some commentators have suggested this reflects the favourable Question Time fallout. However, the poll’s research was conducted on Wednesday, Thursday and Friday last week so it will underestimate the positive effect of both the programme and the manifesto launch which both took place on Thursday.

Scotland on Sunday writers Eddie Barnes and Tom Peterkin were left in no doubt about the Dimbleby effect when they spoke to the well educated and progressive voters of Glasgow’s Byres Road – in the marginal Kelvin constituency the SNP hope to take off Labour. “Quite soon, after just a handful of conversations, some regular themes emerge. Salmond is seen as having done a good job. “Did you see him on Question Time? He wiped the floor with ‘em!” says one West End trendy, wrapped in his Palestinian keffiyeh.”

These sentiments are reflected in the Scotland on Sunday poll questions about leadership, as 42% thought Salmond would make the best First Minister – three times more than Iain Gray on 14%. When the Tory and Lib Dem leaders were taken out, 57% chose Salmond in a straight choice with Gray.

The newspaper also asked about the personal qualities of each man. A massive 60% agreed that Salmond “stands up for Scotland” compared to 15% for Gray. Twice as many thought Salmond was “intelligent” - 40% compared to 18% for Gray. The personality trait where Gray scored highest was “weak”. This was Salmond’s lowest score. But perhaps most revealingly, one in three had no opinion of Gray compared to only one in ten for the First Minister.

It's not just about popularity. Lots of folk like Salmond, but not everyone. However even those who don’t warm to him personally, credit him with strong leadership skills. A stonking majority believe he uses these personal qualities to fight Scotland's corner. This completely undermines a key Labour campaign message. Few Scots believe that Iain Gray, who ran away from protestors and then made a cringe-inducing comment about the killing fields of Cambodia, is a strong leader who can speak for them.

This marks a sea-change in political attitudes. People are proud of Alex Salmond. They like having a First Minister who “wipes the floor” with national politicians on peak time network telly. They are also responding to the very positive message of the SNP, a party which is in business for one reason only – to make Scotland more successful. The party manifesto cover has a single quote from Salmond: “Scotland is on a journey and the path ahead is a bright one. Now is the time for Scotland to keep moving forward.”

This is a view shared by those who are not natural SNP supporters, but who care about the country and fear that a Gray government will return us to the "we're all a bit rubbish" mentality that Labour encourage in Scotland - see Alex Massie in The Spectator..

Kenny Farquharson also reflects the new mood in his column today "Will hope or fear decide the election?" Kenny points out that while Barack Obama and Bill Clinton both won elections with optimistic campaigns “this is Scotland…and we can be grumpy bastards”. In the past, he says, Scotland has voted out of fear and this is what Labour appeal to with their “now the Tories are back” approach. The SNP, by contrast, offer real hope with their commitment to 100% renewable energy generation by 2020 and modern attractive personalities like Alan Cumming and Kick Ass creator Mark Millar. Kenny says the SNP campaign “flatters Scots sense of themselves as a gallus nation that can thrive and prosper, even under darkening skies.” That suggests a country that places hope before fear. So Alex is correct, the path ahead is a bright one.

And on that note let me end by paying tribute to the people of Liverpool and the spirit of optimism, with one of the most feel good songs to come out of that city.