The British referendum this month will determine not only whether the country remains part of the European Union but could also shape the future of the older union of England, Scotland, Wales and Northern Ireland.
Former British prime ministers Tony Blair and John Major have warned that if voters decide to leave the EU on June 23 it could tear the United Kingdom apart because it might spur Scotland to vote for independence.
The thinking goes like this: Scottish voters who want Britain to remain part of the EU would be so unhappy if it decided to break away that they would back a second referendum on forming their own independent nation.
Scottish voters in 2014 turned thumbs down on independence, but popular First Minister Nicola Sturgeon — leader of the Scottish National Party — says a British decision to drag Scots out of the EU against their will could be just the kind of material change needed to prompt a second independence vote.
A variety of polls show that support for remaining in the EU is substantially stronger in Scotland than in Britain as a whole, and surveys suggest that a British exit, or Brexit, would galvanize the independence movement inside Scotland, said John Curtice prominent author of What Scotland Thinks.
"There have been about five polls asking people what they would do now in the event of a U.K. vote for Brexit and on average they show about a 4 or 5 percent swing to those in favor of independence," he said. "That's enough to turn a narrow majority in favor of the union to a narrow majority of around 52 percent in favor of independence."
Prime Minister David Cameron told the House of Commons Wednesday that he worries about a Brexit vote leading to a second Scottish referendum on independence — and a possible breakup of the United Kingdom.
But Brendan Davy, an assistant director of the Vote Leave campaign, dismissed the idea that British exit vote could lead to the breakup of the U.K. He said Remain campaigners are "clutching at straws" with this argument.
"Claims that it could lead to a second Scottish independence referendum are a desperate measure to scare and intimidate people into staying within the EU," he said, adding that many Scottish nationalists also back the Vote Leave effort.
"They must wonder why the SNP is so keen to break away from Westminster but don't want to take more powers back from Brussels. If people want to see the Scottish Parliament get more powers then they should vote to leave the EU."
Then there are those who want to keep Britain inside the EU because they believe that will make it easier for Scotland to obtain independence. They believe that if Scottish voters provide the victory margin that keeps Britain inside the 28-nation bloc, it will anger so many English voters who wanted to leave that it will make it easier for Scotland to gain independence.
Construction worker Andrew Fraser plans to vote this way because he thinks it could be a fast-track to breaking Scotland out of the United Kingdom.
"I'm voting to stay in the EU not because I feel strongly about Europe but because I want independence for Scotland," he said. "If the vote is so close that Scotland keeps England in against its will then the English nationalists will be pushing for us to leave the UK."
His views are typical among some Scottish independence supporters anxious for another chance to end Scotland's 309-year-old political union with Britain.
However, Sturgeon has stopped short of saying any specific result in the referendum would be enough on its own to prompt politicians to call another referendum.
Her party's platform for the recent Scottish Parliamentary election stated a second independence referendum would be demanded only if there was "clear and sustained evidence" the majority of Scots wanted it.
To this end the SNP has announced plans to embark on a new campaign this summer to win the hearts and minds of wavering voters.
James Mitchell, Professor of Public Policy at Edinburgh University, said pro-independence campaigners would likely have to be patient even if the Brexit movement succeeds and Britain leaves the EU.
"Much would depend on the nature of any post-Brexit agreements reached with the EU," he said. "It is likely Brexit would contribute to increased support for independence over the long haul but it may be a slow burner for Scottish nationalists."
If Scotland voted for independence in a second referendum, its leaders have said it would hope to remain part of the EU — or rejoin it if Britain has already left.
But there is no guarantee it would receive the same preferential deal in Europe currently enjoyed by the U.K.
"We would probably be welcomed with open arms but we would have to look very carefully at the terms being offered," said Dr. Thomas Lundberg, Lecturer in Politics at Glasgow University. "It's also possible U.K would offer more favorable terms to Scotland to stay within the U.K. Whatever happens, Scotland could be in a good position to negotiate a better deal with the EU or the U.K."
Despite the extensive coverage of the Brexit referendum, some Scots have yet to make up their minds — and they may drift toward voting in favor of keeping Britain part of the European Union rather than making a change.
"I haven't really thought about it and don't really know what would be best," said David Hammond, a 22-year-old kitchen worker. "I'll probably go with staying in the EU because nobody has really told me, one way or another, what difference it would make if we left."
