Analysis: Scottish independence an iceberg moving toward British leaders

Scottish independence increasingly looks like an iceberg that could sink Prime Minister David Cameron's government and the opposition Labour Party. And like the passengers on the Titanic, they never saw it coming.

Sunday's YouGov poll putting the Yes vote on 51 percent sparked a fresh effort from supporters of the union to urge Scots to come back from the brink. About 100 Labour lawmakers will travel to Scotland this week to campaign for a No vote, while Conservative Chancellor of the Exchequer George Osborne offered more powers over taxes and spending to the Scottish Parliament — if voters opt to stay part of Britain.

Cameron was staying with Queen Elizabeth II at Balmoral Castle in northeast Scotland when he learned that the independence campaign had moved into the lead.

"I've always said that the polls will narrow — it's clearly very tight," Alistair Darling, the leader of the Better Together campaign, which opposes independence, told the BBC. "This is something that's dividing families, friends."

Scottish independence would bring the curtain down on a 307-year-old union that created one of the most influential countries in the world. It would also constitute the biggest crisis of Cameron's premiership.

The prospect of the United Kingdom's demise raises as yet unresolved questions over the future of the country's nuclear deterrent, currently based on Scotland's west coast, and so its diplomatic standing. Yet Cameron was so unconcerned that his office said he didn't watch either of the televised debates between Darling and Scottish nationalist leader Alex Salmond.

After challenging the economic viability of an independent Scotland, the prime minister has mixed that message with an appeal to the shared history of the nations in Britain.

It was a Scot, William Paterson, who founded the Bank of England. Scottish regiments fought Napoleon at Waterloo and the Russians in Crimea. One Scot, Douglas Haig, commanded British forces during World War I, and another, David Stirling, founded the Special Air Service during World War II.

Two of literature's best known Londoners, Dr. Jekyll and Sherlock Holmes, were created by Scotsmen, Robert Louis Stevenson and Arthur Conan Doyle. Bill Shankly at Liverpool and Alex Ferguson at Manchester United were Scots who achieved greatness managing England's most successful soccer teams.

As recriminations began on the "No" campaign, former Labour First Minister of Scotland Henry McLeish told the BBC that his own side had failed to make enough of what the United Kingdom's nations achieved together. "The campaign so far has been narrow, it's been negative, it's also been patronizing," he said. "It's really lacked emotion, lacked passion and lacked soul. So therefore in a country like Scotland where the heart and head are to be taken together that has been a major deficiency."

Three weeks ago, the official message from Better Together was "no complacency." Still, the campaign was comfortably ahead, and an analysis of previous international referendums suggested that electorates generally swung to "No" in the final month. Cameron's principle concern was to push "Yes" below 40 percent and kill the question.

Better Together stopped talking about complacency after Aug. 25, when Salmond won the second televised debate, followed on Sept. 2 by a YouGov poll showing the No lead plunging. Two days later, Cameron was forced to deny he would quit if the vote went against him.

"He could go down in history as the prime minister who lost the union, but I don't think he'll go down in history as the prime minister who was then forced to resign," said Tim Bale, author of "The Conservative Party: From Thatcher to Cameron." "It would be very hard for the party or the press to argue that anything Cameron did or didn't do would have made a difference. He had to allow Labour to make the argument."

The Conservative Party's weakness in Scotland, where it holds one of 59 seats, meant that Better Together has been a predominantly Labour Party affair, with support from the Liberal Democrats. The leader, Darling, is a former Labour chancellor of the exchequer. It is this Labour dominance that explains why, unusually for a crisis for the government, a Yes vote would also be a crisis for opposition leader Ed Miliband.

One problem would be electoral, with Labour facing the loss of a part of Britain that has solidly supported it for more than 50 years, and provided many of its leading figures, including its first leader, Keir Hardy, and former Prime Minister Gordon Brown.

At the 2010 election, Scotland was the only part of Britain where Labour didn't lose seats. With Scotland, Labour has 40 percent of the seats in the House of Commons. Without it, it has 34 percent of them. In the event of a Yes vote, the 2015 election would take place with Scotland still in Britain, but negotiating its exit. Were Miliband to win a majority relying on Scottish seats, his ability to govern would be in question.

"They can only win in 2015 with Scottish seats," said Steven Fielding, professor of politics at Nottingham University. "That would be the worst possible position, with absolutely no legitimacy."

Back with Cameron's Conservatives, there would be little rejoicing at Labour's discomfort, if it came at the price of losing Scotland, according to Bale.

"The union allows Britain to punch above its weight," he said. "It's in the DNA of the Conservative Party that this is a United Kingdom."

-- With assistance from Thomas Penny in London.