The most dramatic findings were in a survey by ICM Research for today’s Sunday Telegraph that put the “yes” campaign ahead by the greatest ever margin, leading the “no” side by eight percentage points, 54 percent to 46 percent, when excluding undecided voters. It came after a poll by Survation for the Better Together campaign put the pro-U.K. group ahead by the same margin. One by Opinium Research for the Observer newspaper showed “no” on 53 percent to 47 percent, while Panelbase for the Sunday Times put the lead at 50.6 percent to 49.4 percent.

The ICM poll putting the “yes” side well ahead “comes with a substantial health warning,” John Curtice, professor of politics at Strathclyde University in Glasgow, said on his blog, citing the small polling sample conducted over the Internet. “The finding, while not wholly disregarded, should clearly be viewed with caution.”

The contradictory polling evidence underscored the volatile nature of the campaign as it enters the final stretch before a ballot that has the potential to trigger the breakup of the U.K. after 307 years and form Europe’s newest sovereign state. Both sides said their door-to-door canvassing showed they were ahead.

Banners, Balloons

On the final weekend of campaigning, activists were out in force across Scotland with “yes” stands handing out stickers competing with “No, Thanks” banners and balloons.

In Edinburgh, there was a march yesterday by thousands of Orange Order members to rally support for the union, while Glasgow’s main shopping thoroughfare was taken over by a mass demonstration in support of independence.

“We will win and I know that because I can see our returns,” said former Chancellor of the Exchequer Alistair Darling, who fronts the Better Together group. “We will win, be in no doubt about it.”

Yes Scotland welcomed its lead in the ICM survey, though said it just confirmed the race would go down to the wire.

“Taken in the round, the polls show that the referendum is on a knife edge,” Blair Jenkins, chief executive of Yes Scotland, said by e-mail. “There is everything to play for, and this will spur on everybody who wants and is working hard for a Yes to redouble their efforts.”

Cameron Campaigns

Conservative Prime Minister David Cameron is due in Scotland again tomorrow as the main U.K. parties that oppose independence and the nationalists led by Scottish First Minister Alex Salmond compete to persuade undecided voters.

A separate ICM poll for the Guardian two days ago that put “no” ahead found 17 percent of voters saying they had yet to make their minds up. YouGov, in a Sept. 11 poll, put the undecideds on 6 percent, while TNS earlier in the week had 23 percent undecided in a Sept. 9 poll.

That variation reflects the difficulty of conducting polling for a referendum, where there isn’t a past voting record for calibration. Women backed staying in the U.K. by 55 percent to 45 percent, while men favored independence by 52 percent to 48 percent, the ICM poll for the Guardian showed.

The tightening of the race in its final fortnight has led to increased volatility in the financial markets, with forecasts the pound could tumble in the event of a “yes” vote.

While the government denies it is preparing contingency plans for the referendum outcome, signs of the concern are growing. Bank of England Governor Mark Carney has said he will return early from a gathering of central bankers and finance ministers in Cairns, Australia, so that he can be in London in time for the vote. Chancellor of the Exchequer George Osborne canceled his trip.