London (AFP) - Scotland's first postal ballots for a referendum on independence headed to voters on Tuesday after the leader of the campaign to break away from Britain scored victory in a final TV debate.
One-sixth of the Scottish electorate -- some 700,000 people -- could receive their polling papers as early as Wednesday, and begin answering the question: "Should Scotland be an independent country?"
The rest of voters will have to wait until September 18 for the historic referendum that could end a union dating back to 1707.
A "Yes" victory would create Europe's first independent state since the disintegration of Yugoslavia and leave both sides of the split in uncharted political and economic waters.
British politicians have promised Scotland will be given greater autonomy -- in particular with increased taxation powers for its government -- even if the "No" camp wins.
The independence campaign has lagged in the polls despite recent advances, and was hoping for a boost from Monday's strong debate performance by Scottish First Minister Alex Salmond.
In a snap Guardian/ICM poll following the ill-tempered exchange, 71 percent of respondents said that Salmond, leader of the Scottish National Party (SNP), had bested his opponent, former British finance minister Alistair Darling.
But experts questioned whether a debate performance would influence voting intentions.
"Whether [Salmond] has done enough to move the numbers, I think, may be another question," John Curtice from Scotland's University of Srathclyde told BBC News.
As of last week, 57 of respondents in a YouGov poll for The Times said they would vote for Scotland to remain part of Britain, against 43 percent who would say "Yes" to the split -- a 14-point spread.
- Currency question -
The two rivals clashed on topics that ranged from what currency an independent Scotland would use to oil reserves, from defence to the fate of the National Health Service (NHS).
Darling was quick to bring Monday's debate to the question of what currency an independent Scotland would use -- perceived as a weak point for the "Yes Scotland" campaign in the past.
But Salmond said a vote for independence would give him a mandate to demand a currency union with the rest of the United Kingdom, an idea that the three main parties in Westminster have rejected.
Darling then accused Salmond of talking "nonsense" over estimates of revenues from North Sea oil, which would be the lifeblood of an independent Scotland.
Darling argued that staying in Britain would guarantee jobs, but appeared to falter as Salmond doggedly questioned him on what powers Scotland would be granted to create jobs in the future.
Both were challenged by members of a lively audience of 200.
- Defining decision -
The debate also touched on the fate of the British nuclear programme Trident, under which missiles are stored in a Scottish naval base.
Salmond said an independent Scotland would reject nuclear weapons, which he called a "waste of money as well as being morally wrong" -- but was criticised by an audience member concerned about the risk to jobs.
The debate later turned to discussion of the NHS, when Salmond argued that a split with the rest of Britain would protect Scotland from cuts to health spending, while Darling insisted that funding for the service was due to rise.
Summing up the case for unity, Darling said: "We do not need to divide these islands into separate states in order to assert our Scottish identity."
But Salmond said that independence could guarantee that "at each and every election in an independent Scotland we will get the government that we vote for".
"The decision we make in three weeks' time will define us," Salmond said. "It's an opportunity which may not come our way again."