The SNP says independent Scotland would be entitled to 90 percent of revenue from North Sea oil and gas — which stood at 6.5 billion pounds ($10.4 billion) in 2009-2010 — but only liable for 8 percent of 1 trillion pound ($1.67 trillion) national debt, based on Scotland's share of the U.K. population. The British government disputes that breakdown.
Pro-union politicians also claim Scotland lacks the economic clout to go it alone, pointing out that its two biggest financial institutions, the Royal Bank of Scotland and the Bank of Scotland, are now largely owned by British taxpayers after nearing collapse during the 2008 global banking crisis.
Then there are factors beyond the U.K.'s borders. Europe's crisis is boosting breakaway movements across the continent, from Belgium's Dutch-speaking Flanders to the Spanish region of Catalonia, whose regional parliament has voted to hold a referendum on self-determination.
"I don't want independence and I am concerned that people will think if Catalonia can do it, so can we," said David Mackenzie, an insurance salesman from Edinburgh.
For now, the "Yes" campaign — a loose coalition that includes Greens and Salmond's SNP — has the momentum. Its slick campaign effectively uses social media such as Facebook and Twitter to mobilize support.
The pro-union "Better Together" campaign, which includes both Cameron's Conservative Party and its arch-rival Labour, has had a lackluster start.
Political commentator and former Labour spin doctor Simon Pia said the pro-union side needed to raise its game.
"The SNP has stolen a march with its campaign which is very savvy and concentrates on positive reasons to split," he said.
He said pro-union forces "need to offer a vision of positive and emotional alternative to independence and not just focus on the negatives of the impact of separation."
Lawless reported from London. Jill Lawless can be reached at http://Twitter.com/JillLawless
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