Nicola Sturgeon, Scotland’s longest serving first minister, resigned earlier this year in a move that confounded many political observers at the time. On Sunday, she was arrested by police investigating allegations of financial misconduct. Sturgeon, who led the Scottish National party to electoral domination at Holyrood – the home of the Scottish parliament – was questioned by detectives “as a suspect” but was later released without charge, pending further inquiries, after voluntarily going to a police station. Who is Nicola Sturgeon? Sturgeon was a rare political constant during a turbulent era in British politics. During her tenure as first minister (the title given to the head of a devolved government in the UK), four UK prime ministers resigned as did two main opposition leaders at Westminster. As one of the few female world leaders, Sturgeon became internationally recognised. In 2016, she was ranked the second most powerful woman in the UK after Queen Elizabeth II by Forbes. Her political demise has been swift. She was first elected as an SNP member of parliament in 1999 and was elected deputy leader in 2004 on a joint ticket with Alex Salmond, who became SNP leader. Sturgeon became the de facto leader of the opposition in the Scottish parliament as Salmond was an MP in Westminster, not an MSP in Holyrood, and was not able to take up the role. In 2007, Salmond was elected to Holyrood following that year’s Scottish parliamentary elections, which were an electoral breakthrough for the SNP. He became the first minister with Sturgeon serving as deputy. In 2011, the SNP scored their best electoral achievement ever, winning an absolute majority in Holyrood, the only party ever to do so since devolution in 1999. Salmond and Sturgeon were re-elected into their respective roles. The party had committed in its manifesto to hold an independence referendum. David Cameron, then the prime minister of the UK, agreed a deal with the Salmond administration in 2012 to hold an independence referendum. The vote was held in 2014 when 55% of Scots voted to stay in the union. Salmond resigned as a result. Sturgeon announced her run to become SNP leader without an opponent coming forward. She became the party’s first female leader and thus first minister unopposed. Why was she arrested? Her arrest was shocking but not entirely unexpected. Fifty days after her resignation, Peter Murrell, Sturgeon’s husband and a former SNP chief executive who had resigned his position weeks earlier after claiming “responsibility” for giving false party membership numbers to the media, was arrested as part of Operation Branchform, a Police Scotland investigation into allegations that more than £600,000 in donations for an independence campaign was misspent by the party. Large forensic tents were erected outside the couple’s home, which provoked a furious response from her allies. Colin Beattie, an MSP and the SNP’s treasurer, was arrested less than two weeks later as part of the investigation. He resigned as party treasurer the following day. Sturgeon is the third senior SNP figure to be arrested as part of the operation. What does it mean for Scottish independence? Polling on the question of Scottish independence has remained largely unchanged since Sturgeon’s resignation. There has not been a major dip since Sturgeon’s successor as SNP leader and first minister, Humza Yousaf, took over. In fact, an Ipsos/STV poll carried out in May found that 53% of Scots support independence. However, difficulties may lie in falling support for the SNP. The party’s vote share was 26 percentage points ahead of the Conservatives in the 2021 Scottish parliament elections. Recent polls put its lead over the Scottish Labour party in single or low-double digits. Apart from the Scottish Greens, no other major opposition parties support an independence referendum. If the SNP loses its dominance at Holyrood, the likelihood of another independence referendum greatly recedes. What could happen next? After Sturgeon’s arrest on Sunday, her internal critics inside the SNP and opposition leaders have called on her to voluntarily stand down as an MSP or for Yousaf to suspend her pending the outcome of the police investigation. She has denied any wrongdoing, issuing a statement on Sunday night declaring: “I know beyond doubt that I am in fact innocent of any wrongdoing.” Yousaf has refused to take any disciplinary action against her because she has not been charged with any offence. He said he believes people should be treated as innocent until shown to be guilty. The police investigation continues. Police Scotland has never disclosed exactly what it is investigating nor released the name of the lead detective. Earlier this month, the force’s chief constable, Sir Iain Livingstone, said the search of Sturgeon’s home was “proportionate and justified”. The police investigation, he said, had “integrity” and “rigour”.