The buskers in Glasgow's Buchanan Street momentarily switched to an upbeat pop anthem as the crowd of more than 100 or so young people gathered below a statue of the father of the Scottish parliament, Donald Dewar.

They are here to launch Generation Yes, the latest grassroots pro-independence group, this one for younger voters. Saffron Dickson, a 16-year-old schoolgirl, is one of the driving forces. "We're not established politically, we're not seasoned by it all, but our energy is just so vast, it's all so positive because it's all about the future," she gushes, waving multi-coloured polished nails. "Young people are more informed than anybody thinks and ohmigod we just want to tell people don't be scared!" Dewar might not have approved, but shoppers stop to smile at their enthusiastic cheers.

Here at least there's a feeling of momentum gained and everything still to fight for. It's this palpable "buzz", along with the creeping closer of both sides in the polls, that has started to worry David Cameron, Nick Clegg and Scottish secretary Alistair Carmichael.

This weekend Scottish Lib Dems heard their leader, Willie Rennie, tell the party conference in Aberdeen that they had to turn the pro-UK "project fear" into a "sunshine" strategy. It's a big ask for the Better Together campaign, which is coming from the grammatically negative no position. With six months until the Scottish referendum, there is a distinct shifting of the tempo and this is without doubt a stage of the electioneering marked by an extraordinary energy in the yes camp.

In the elegant Better Together offices in Blythswood Square, Glasgow, they say they are not bothered by all the razzmatazz of the other side, but are concentrating on serious issues. They had David Bowie after all, and Eddie Izzard is doing a show in Edinburgh next month to support the no vote.

Better Together deny they're lacking sunshine. "What can be more negative than seeking to create barriers and divisions between people where none exist, as the nationalists want to do?" says campaign director Blair McDougall. "While the nationalists are increasingly speaking to each other, we are on the doorstep talking to undecided voters about the things that matter to them – what would replace the pound, what would happen to pensions, and the increases in the cost of living if we leave the UK.

"We have a positive vision for Scotland and believe we can have the best of both worlds, a strong Scottish parliament, with the guarantee of more powers, backed by the strength, security and stability of being part of the larger UK."

The British government's "no currency union after independence" position was buffeted at the weekend after a minister told the Guardian that an independent Scotland could keep the pound, while a poll by the Times showed 45% of Scots thought George Osborne's threat over sterling was a bluff to begin with.

Alistair Darling, the leader of Better Together, has always said that Scotland is perfectly capable of running its own affairs, but the no voters are still waiting for real offers from all the parties in Westminster.

The yes campaign complains that it cannot get Better Together representatives to join them on debating platforms, but it seems that Better Together has decided public meetings are not the way to reach the "missing million" of undecideds, most in the bellwether Glasgow area. Many voters will not be rushed on this momentous decision, and there's a long way to go until 18 September.

But something has changed, says journalist and author Lesley Riddoch of Nordic Horizons, a thinktank examining why Scotland's Scandinavian neighbours of a comparable size are doing so much better. Its work was never meant to be framed by the independence debate. "I'm yes and my co-founder is no, but the referendum wasn't on the cards when we set out. When we started we couldn't get the Scottish government to fund us a taxi fare," she says.Her new book, Blossoms: What Scotland Needs to Flourish, is a polemic on disenfranchised Scots turning away from top down power and an analysis of how better democracy could be achieved, in or out of the union.

"Now, of course, the tremendous energy brewing in completely different parts of Scottish society has increased interest. At the moment that incredible buzz is around the independence side, that's unquestionably true. And it is right that Better Together has been incredibly lacklustre. But people on both sides of the argument are doing a phenomenal unpacking of things and looking at them again. You can get bitter and twisted about the past or get infected with that fresh energy."

Blair Jenkins is chief executive of the yes campaign: "We said from the beginning that it was about grassroots campaigning. People were asking us what they could do and we said convert one other person. So I get people in the street shouting their conversion rates at me.

"We're in a media landscape where we struggle to get parity of coverage, so we decided the best way was our own way, going into communities, talking to people face to face and digitally.

"Everybody now believes there will be a high turnout, and that's an achievement in itself.Getting people to question the roadblocks being put in their way is another. This is bigger than politics; people who have tuned out of politics are tuning into this. A whole lot of people will have got the bug for a passionate and authentic debate. Meetings are packed, some are like football matches. We're finding it hard to get people from the no side to share a platform with us, so we have to do it ourselves."

Both sides have closely studied the Barack Obama model, that first presidential election which caught fire through a grassroots and digitally led campaign leaving the mainstream TV politicos struggling to catch up.

Better Together has employed Blue State Digital, one of the companies that worked on Obama's "yes we can" campaign. Both sides claim 250 local groups are out campaigning, although just a glance at their respective website listings show a big difference in the types of events. Yes are at the helm of what's being called the "town hall revival" –roadshows and meetings, debates in schools. Better Together is going for the stealthier, traditional approach – maildrops and door knocking.

William Bain is certainly not a man anyone could accuse of complacency. The Labour MP for Lambhill in Glasgow knows estates like these are where many of the missing million live. Three times a week he knocks on doors to tell them why they should vote no. He says he's eschewing the big meetings and debates because "you can do a debate and maybe get 20 or 30 people; a few hours of this and you'll have spoken to treble that amount".

He has six volunteers today. Does he feel the campaign is negative and lacklustre? "By its nature I have to talk about a lot of things we can't do, but it's a tough fight. Ed Miliband is doing a great job in what we can do as a united kingdom. But the important thing is that people are starting to talk about it, in workplaces, sports clubs and at home. I read Hillary Clinton's book about how she went out door to door every day with her aide and how she persuaded people, that's how she won upstate New York.

"It's remarkable that the energy has maintained itself at the level it has, bearing in mind that really the campaign started in 2012," says Bain. "It's unprecedented to have such a long runup. And Scottish politics is very competitive; Scotland being Labour is no longer true. But there's very much a new sense of talking about politics."

Not many people are keen to talk today, although plenty are nodding their intention to vote no before closing their doors against a wind that burnishes the cheekbones. Lambhill is an estate on the edge of the city with the Campsie hills rising beyond, and the weather is of the type that forces the shoulders up to the ears, and the six volunteers move quickly, hands red over clipboards. One householder talks about bankers' bonuses and complains about the growing queues at hospitals, losing his sickness benefit even though epileptic seizures meant he had to stop work as a driver. He's not happy with "David Cameron and that lot", who don't know what it's like to live on the breadline, but he's giving Bain his no vote. "Actually, men in their 30s and 50s are usually more disposed as yes, while women want to take time to look at it practically."

Melissa McCartney, 32, opens her door to John Kane, 74, from the Gorbals, who took up canvassing for the Labour party in his retirement, and the two have a friendly chat. "I'm yes," she tells him. "I'm following my heart, because politically it's one puppet or another puppet and this is a chance to change that. Women in my work are still thinking about it, they're a bit scared, they're back and forth right now."

Kane nods: "They're a bit feart, and they should be." He decides McCartney might change her mind, however confident she sounds. He could be right, confidence is easy to knock and a lot can happen in six months. But as Dickson and her Generation Yes mates go skipping off leafleting, a no vote is unlikely to stop these new campaigners wanting a different Scotland.