As the yes campaign reached 47%, signs of a switch by women, who polls showed had been supporters of the union, could be decisive

Less than three weeks before the referendum on Scottish independence, the forces of nationalism have suddenly appeared on the final bend of the campaign race and are picking up the pace.

One poll last week put the yes vote on 47%, but the "no" campaign has been quick to point out that, as every previously published poll has shown, they still hold the lead. However, the gap has never been so small. The momentum appears to be with the yes campaign. The bounce in the yes vote may be no more than to be expected following Alex Salmond's besting of Alistair Darling, leader of the Better Together campaign, in last Monday's televised head-to-head debate between the two. Such increases in these circumstances are fragile and can easily evaporate. Scotland, though, has been here before.

In 2011, a few weeks before the Holyrood election, Labour held a healthy, double-digit lead over the nationalists. Within a few weeks that lead was wiped out in a gargantuan swing which returned Salmond as first minister and gave his party a clear overall majority, something Scotland's post-devolution voting engineering had been supposedly designed to prevent. This time, yes activists are beginning to believe lightning might strike twice. They claim to be polling particularly well in solidly working-class enclaves, the very ones that rejected Scottish Labour three years ago.

In one of those enclaves, a community hall in Govan on the southern banks of the Clyde, members of another social constituency are also having their say. These are the women who frequent the Tea in the Pot drop-in centre, 14 of whom have gathered to discuss independence issues with the Observer.

The women of Scotland may yet hold the key to victory in this campaign. At the outset, there was a clear majority among them for the no side, a consequence, it had been thought, of Salmond's unpopularity among them.

Soon a debate is under way. These are strong women who have perhaps encountered some pain and mistreatment in their lives. They express their frustration that, despite invitations to both the yes and no camps to organise an all-women panel debate on independence, no response has been forthcoming from either side.

Voting intentions among them show yes has a lead of nine to five. Three – all of them yeses – have already used their postal vote. Every one of the others intends to vote on 18 September.

They express eloquent frustration at the lack of women in politics, though each knows about and admires Nicola Sturgeon, deputy first minister and one of the local MSPs. Soon a well-informed exchange about the "bedroom tax" and food banks is under way. "Even people in work are using these because they're not being paid enough to run a family and their benefits are being cut or are deliberately delayed," I'm told.

Their top three issues are: privatisation of the NHS; the challenges faced by single-parent families; and properly paid jobs for young people. One of the senior members of the group, Ruby, is a confirmed no voter: "I love the UK and, over the years, it's been good to me. I would hate to see the breakup of the kingdom."

A younger woman with children and stepchildren dismissed all the UK celebrities who have been love-bombing Scotland: "They always used to say we were a drain on resources and didn't pay our way. Now they can't get enough of us."

The great debate that has swept Scotland in recent months, across all social classes, is about to reach its climax. Time is running out in the battle to win over the undecided in places like this community centre. In the 18 days that remain of the campaign, two events may yet have a crucial bearing on the outcome.

The first is on 5 September, when STV hosts its second live debate which will feature two panels of three prominent figures from each side. Speaking for Yes are Nicola Sturgeon, Scottish Green Party co-convener Patrick Harvie MSP, and actress Elaine C Smith. The No team will be Labour shadow foreign secretary Douglas Alexander, Scottish Conservative leader Ruth Davidson, and Kezia Dugdale, Labour MSP.

Then on 13 September, the last Saturday before the vote, comes an event which has elicited delicious discomfort in both camps, when the Grand Orange Lodge of Scotland is organising a march of up to 15,000 of its members through Edinburgh in support for the union.

Privately, some in the no camp are dreading this event for fear that it may drive some undecided Catholics into voting yes, while the nationalist camp has simply refrained from making any comment in case it antagonises a significant and committed 50,000 membership body which feels it has a dog in this fight and, like all other participants, has a right to express its views. The next three weeks are certainly going to be lively.