THE train hadn't even pulled away from Queen Street station before a beaming Chris Stephens, one of the SNP's candidates in next month's European elections, had presented me with a Partick Thistle for Yes badge.

"They are going down a storm," he said cheerfully as I admired the red and yellow button. "We had 200 made but we've had to order another 500. They are £1 but I'll not charge you."

The 16.41 taking me to Aberdeen and the final, frenzied SNP conference before the referendum duly set off. But I'd not got far before I had another story to think about. At Perth, Nationalist MSP Chic Brodie hopped on and was soon chatting about the Yes campaign in Ayrshire. He told me about the regular "Pint, Pie and a Yes" get-togethers in a Prestwick pub. "They are packed," he said. Not only that, he added with a mixture of delight and surprise, some well-kent local Labour folk had turned up - and signed up.

Such tales from the frontline of the referendum campaign are the currency of this conference, traded freely and swapped enthusiastically in the coffee shops away from the main hall.

They confirm, as if the train journey hadn't already, everything I was briefed about by a senior SNP strategist before I set off. "Something is happening like never before," the insider said. "There are lots of people out talking to lots of people across the country and what is significant about this conference isn't the business in the hall, it's not the speeches, it is activists meeting each other, discussing what they are doing, what's working, exchanging ideas."

Chatting with SNP members in Aberdeen it's hard to believe the Yes campaign is behind in the polls. Two surveys published on the eve of the conference put the No side's lead, when don't-knows were excluded, at six percentage points and 12 points respectively. They suggested the narrowing of the gap witnessed since the turn of the year had stalled and support for both Yes and No had stabilised. But as one party staffer told me: "If you'd told us in October this would be the position we'd have bitten your arm off. Then, in my heart of hearts, I hoped we'd win. Now I believe we will win."

One factor is the breadth of the Yes campaign. Initially wary SNP diehards have found themselves enjoying campaigning alongside Greens, SSP members and - above all - people who have never previously been active in politics.

Quite simply, it's given them a lot more firepower. Old hands remember all too well the party spending a fortune to produce its own newspaper during the 1999 Scottish Parliament election - then finding they had no-one to deliver the copies.

Even in the victorious 2007 and 2011 campaigns the effort on the ground was much smaller than it is today. "Since the turn of the year activity levels have gone through the roof and that's when the polls started to move," the strategist said. "Everyone now is working at general election tempo and we are still five months out from the vote."

It might be wise to inject a note of caution at this point. If senior party figures are briefing a story of massive grassroots activism, it's because they want journalists to write it. Why wouldn't they? It creates a sense of momentum, that most crucial of political commodities. The ground war, supposedly invisible to the media, then becomes part of the air war, the high-profile battle played out in the newspapers, on radio and on television.

Perhaps all the Twitter trails celebrating "super Saturday" days of action, coffee mornings and "undecideds meetings" are a mirage, just so much cyber chaff thrown out to confuse the radar and create an exaggerated impression of activity. But I doubt it. If the Yes campaign is trying to kid us on, they are also fooling the folk who should know what's happening, their own foot soldiers. Worryingly for the pro-UK side, the story unfolding on Twitter is more likely to be the tip of the iceberg.

The sense of determination and, above all, the belief within the SNP, should give their opponents pause for thought. Perhaps it's time Better Together called in at the Pleasant Field bar in Prestwick or any of the hundreds of other venues hosting Yes events. If they want to go in disguise, a Partick Thistle for Yes badge only costs £1.