The Scottish National Party, which has led a minority government since 2016, says a big victory will give it the moral right and political momentum to hold a referendum on whether Scotland should end its three-century union with England.
Scotland votes in an election that could trigger a showdown with British Prime Minister Boris Johnson over a new independence referendum just five years since the Brexit vote strained the United Kingdom to breaking point.
Scotland is home to one of the world's most prominent independence movements and Scottish First Minister Nicola Sturgeon has described this election as the most important in the country's history.
Sturgeon, who leads the pro-independence Scottish National Party, or SNP, has vowed to demand legal powers for another referendum by the end of 2023 if her party wins a majority in the 129-seat devolved parliament in Edinburgh.
All the opinion polls suggest the SNP will win a fourth term in office, but they also indicate a recent dip in support for her party, suggesting that her chances of winning a crucial outright majority are too close to accurately call.
The only time the SNP has won a majority before was in 2011. Britain's then-Prime Minister David Cameron bowed to pressure and agreed to a referendum in 2014. Scots then voted by 55-45 percent to remain in the more than 300-year-old union.
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🤲 Scotland's future is in your hands tomorrow, re-elect @NicolaSturgeon so we can get on with the serious job of delivering Scotland's recovery.— The SNP (@theSNP) May 5, 2021
🗳 Don't risk letting Boris Johnson have control after Thursday, make it #BothVotesSNP.
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Although the last independence referendum was meant to settle the matter, Britain's departure from the European Union, a perception that Scotland's government handled the Covid-19 crisis well, and antipathy to the Conservative government in London have bolstered support for going it alone.
If there was another referendum and the Scots voted to leave, it would mark the biggest shock to the United Kingdom since Irish independence a century ago. It would mean the United Kingdom would lose about a third of its landmass and almost a tenth of its population.
On Thursday, Scotland will elect all the members of its semi-autonomous parliament, known as Holyrood, which has control over areas such as healthcare, education and some taxation. The British government says the law means that Scotland would require the permission of the British parliament to hold another referendum legally.
Prime Minister Boris Johnson has said he will turn down any request because the issue was settled seven years ago.
"The desire for Scottish independence has been growing for a considerable amount of time," said Anthony McGann, a professor of politics at the University of Strathclyde.
"If you have a Scottish government asking for a referendum and a UK government not willing to grant one, it is going to put an enormous strain on the existing constitutional structure."
🗳 It really is on a knife edge. If you want an @theSNP government and First Minister with the strength and experience to immediately get on with the job of leading Scotland through the crisis and onto recovery, please make it #BothVotesSNP tomorrow 🗳 🙏 https://t.co/X2WQvZFaeb— Nicola Sturgeon (@NicolaSturgeon) May 5, 2021
The SNP have said they plan pass legislation to hold a new referendum by the end of 2023. They will then dare the British government to challenge the decision in the courts.
Polls in Scotland will open at 0600 GMT and will close at 2100 GMT. Normally, the results are announced overnight with counting started soon after voting close.
But the coronavirus pandemic means that the votes will not be counted until the following morning. Just over a third of the results will be announced on Friday and the remainder will be announced on Saturday.
Earlier this year, polls suggested Sturgeon, who was widely praised for her honesty and grasp of detail during the coronavirus pandemic, was on course to win a record majority in the elections.
But she has been involved in a bitter feud with her predecessor, Alex Salmond, over the handling of an investigation into sexual harassment allegations against him.
Salmond started his own pro-independence party in March and the row has cast an unflattering light on the independence movement tainted by in-fighting.
Even if the SNP fails to win a majority, Sturgeon could still call for another referendum if there is a majority of pro-independence parties in the Scottish parliament. The Greens, which back a new referendum, have supported the SNP in government and could provide Sturgeon with the lawmakers to argue for another poll.