The battle over Scotland’s future in the U.K. entered the final day of campaigning with the pro- independence side saying it had the momentum to win the ballot and the “no” camp urging voters not to use it as a protest.

Three polls last night showed the anti-independence Better Together group backed by Prime Minister David Cameron and the main U.K. parties leading the “yes” campaign by 52 percent to 48 percent, excluding undecided voters. All the latest surveys showed the gap was closing fast.

Scottish First Minister Alex Salmond will make his final appeal to voters to embrace independence today as he attempts to snatch victory in the last 24 hours of the two-year campaign. Opponents of independence canvassed through the night into the early hours, visiting late shift workers in hospitals and at a print works.

“It is very tight,” John Curtice, professor of politics at Strathclyde University in Glasgow, was cited as saying in the Scotsman. “It looks as if the ‘yes’ campaign is going to fall agonizingly short from their perspective. But I have always said this is the ‘no’ campaign’s to lose and it certainly looks as if they have got pretty close to that.”

Former Labour Prime Minister Gordon Brown and Alistair Darling, the ex-chancellor of the exchequer who leads the Better Together campaign, will hold a rally in Glasgow today. Salmond will visit an engineering business outside Glasgow before addressing a closing event this evening in Perth, central Scotland.

‘Empowering Moment’

“Don’t let this opportunity slip through our fingers,” Salmond, who heads the semi-autonomous government in Edinburgh, said in an advance copy of a letter to voters. “It’s the greatest, most empowering moment any of us will ever have.”

Better Together gained more celebrity backing with former U.S. President Bill Clinton’s announcement in a release last night that he wanted Scotland to stay part of the U.K.

“If we vote to go tomorrow, there’s no going back,” Darling said in an interview with BBC Radio 4 today. Both sides were agreed that the referendum should decide Scotland’s place in the U.K. without a repeat vote, he said.

“This is to settle the matter for a generation,” Darling said. “Because I don’t think there’s any appetite in Scotland for another referendum.”

After a weekend of polls showing contradictory findings, the convergence of the three latest three surveys -- by ICM for the Edinburgh-based Scotsman, Opinium for the Daily Telegraph of London, and Survation for the Daily Mail -- underscores how close the result could be in the Sept. 18 ballot.

Pound Stable

Amid the threat of political and economic volatility, the pound was little changed in London trading today. Since slumping to a nine-month low of $1.6052 on Sept. 10 after a YouGov poll showing the “yes” campaign ahead for the first time, sterling has gained 1.5 percent to $1.6295 today.

The Spanish government, struggling with its own secessionist movement in Catalonia, stepped up its resistance to the Scottish referendum, with Prime Minister Mariano Rajoy saying that independence votes were damaging for the European Union. Foreign Minister Jose Manuel Garcia-Margallo went further during a parliamentary debate in Madrid today.

“Secession would be a catastrophe for Scotland,” Garcia- Margallo said. “It would start a process of balkanization that nobody in Europe wants.”

Polls Narrow

The ICM poll represents an increase of three percentage points for the pro-independence camp from a similar poll in August and a drop of the same margin for those who reject ending the U.K. When including the 14 percent of respondents who said they had yet to make up their mind how to vote, the lead for the “no” campaign was 45 percent compared with 41 percent for the “yes” campaign.

The four percentage-point gap found in the Opinium poll narrowed from six points in the company’s last poll, for the Observer newspaper, published at the weekend.

Survation’s results from fieldwork done Sept. 12-16 showed support for the “yes” campaign had increased by two points as a smaller proportion of people were undecided, leaving the gap at 48 percent to 44 percent in favor of the U.K. when all respondents were included.

When the latest findings were included, a poll of polls compiled by Curtice at Strathclyde put the “no” lead at two points, 51 percent to 49 percent for the “yes” side.

“We are in touching distance of success on Thursday,” Blair Jenkins, chief executive of Yes Scotland, said in a statement. “We are working flat out to ensure that we achieve a ‘yes’ vote, because it’s the biggest opportunity we will ever have to build a fairer society and more prosperous economy.”