When Scotland’s longtime leader Nicola Sturgeon announced her shock resignation in February, no one would have guessed that just four months later, she would be pictured in the back of a police car. The former First Minister and Scottish National Party (SNP) leader was arrested on Sunday amid an ongoing investigation into the funding and finances of the SNP. After several hours of questioning, Sturgeon was released without charge.

“To find myself in a situation I did today when I am certain I have committed no offense is both a shock and deeply distressing,” Sturgeon wrote in a statement posted to Twitter following her release. “Innocence is not just a presumption I am entitled to in law. I know beyond doubt that I am in fact innocent of any wrongdoing.”

The arrest marks a dramatic fall from grace for Sturgeon, a once-towering figure in British politics who dominated Scotland’s independence movement for nearly a decade. Although her successor Humza Yousaf has so far avoided implication in the ongoing probe, neither he nor his party have been insulated from the blowback. The scandal has sent the SNP into internal disarray, with some of its members now calling for their former leader’s suspension. The party’s standing in the polls, though better than that of its rivals, has seen a marked dip in recent months. A recent Survation survey found that 41% of SNP voters are less likely to vote for the party as a result of the investigation.

Below, what you need to know about the investigation and its implications for British politics.

What is the police investigation about?

Operation Branchform, as Police Scotland’s investigation into the SNP’s finances is known, first began in 2021 over complaints of alleged mishandling of more than £600,000 ($750,000) in donations earmarked for securing a second independence referendum.

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The first, which was held in 2014, resulted in Scots voting 55% to 45% to remain in the U.K. But independence campaigners argue that support for independence has only been bolstered by Britain’s exit from the E.U., which the majority of Scots opposed.

Central to the investigation are allegations, first raised in 2017, that donations earmarked for another referendum were instead used by the SNP to finance its general election campaign in 2017—a claim that the party has staunchly denied. Those allegations only grew louder in 2020, after the U.K.’s Electoral Commission published the SNP’s 2019 accounts, which revealed that the party had just under £97,000 in the bank—a far cry from the £600,000 it claimed to have “ring-fenced” to fight for another referendum. The next year saw a number of high-profile resignations from the party over transparency issues, including the SNP’s national treasurer.

In June 2021, the SNP’s longtime chief executive (and Sturgeon’s husband) Peter Murrell provided the party with a personal loan of £107,000 ($133,000) to “assist with cash flow.” One month later, Police Scotland formally launched its investigation.

Though it remains unclear how much Sturgeon knew about the status of the investigation prior to her resignation, her decision was swiftly followed by the resignation of her husband, who stepped down as the SNP’s CEO after taking responsibility for misleading the media about the party’s membership figures, which saw a sizeable drop from its peak of 125,000 in 2019 to 72,000 in 2023. (A decline that is estimated to have cost the party hundreds of thousands of pounds in lost income generated by membership dues.) Like Sturgeon, both Murrell and the SNP’s erstwhile treasurer Colin Beattie were arrested and taken in for questioning before ultimately being released without charge, pending further investigation.

Among the most surreal moments of the investigation—at least prior to Sturgeon’s arrest—was the police’s decision to search her and Murrell’s home as well as confiscate a luxury motorhome worth an estimated £110,000 ($137,000), which had reportedly been purchased as a “battle bus” for the Scottish elections in 2021 and was, at the time of confiscation, parked outside Murrell’s mother’s house.

What impact has the investigation had on the SNP?

The SNP has been in turmoil following Sturgeon’s resignation. The race to replace her exposed deep divisions within the party on matters as wide-ranging as gender-recognition reforms and how best to achieve a second independence referendum, and even prompted speculation of a potential split within it. While Yousaf’s victory was welcomed by the SNP leadership, his brief tenure has largely been overshadowed by the ongoing investigation. His status as the “continuity candidate” has made it difficult for him to distance himself from Sturgeon, who only days before her arrest he described as being “one of the best” politicians Europe has seen in decades.

Though the arrest of former political leaders is highly unusual in Britain, Sturgeon is not the first former First Minister to be taken into police custody. Indeed, her predecessor Alex Salmond, who led the SNP into government in 2007, was arrested—but ultimately acquitted—on sexual assault charges in 2019.

Will the investigation hurt the SNP’s independence aspirations or electoral prospects?

The investigation into the SNP’s finances has been ongoing for some time, with an unclear impact on the public’s overall support for the party’s signature goal of Scottish independence. According to What Scotland Thinks, a blog run by British pollster John Curtice and the Scottish Centre for Social Research, support for Scottish independence has oscillated between 45% and 55% in recent months, with the most recent polling showing support for independence trailing those against 45% to 48%, respectively.

The same may not be true for the SNP’s electoral prospects, however. The ascendant Labour Party, which is leading national polls, is hoping to make gains in Scotland when Britain holds its next general election, expected in late 2024. In addition to being the largest political party in Scotland’s devolved legislature in Holyrood, the SNP also claims the majority of the majority of Scottish seats in the U.K. national government in Westminster. As things stand, the SNP is at risk of losing half of its Westminster lawmakers to Labour, according to recent projections from the British pollster YouGov, in what would be the party’s worst performance since 2010.

Write to Yasmeen Serhan at yasmeen.serhan.com.