When Jacinda Ardern resigned as New Zealand’s prime minister a few weeks ago, Nicola Sturgeon assured voters she still had plenty left in the tank. Yet apparently, Scotland’s first minister had been thinking about her own future for some time. She said so in her resignation speech last Wednesday, which came as a surprise to much of Scotland.

Despite a recent and consistent wave of difficulty and controversy over the gender recognition reform bill, the quest for another independence referendum, a finance investigation into the SNP and an ongoing “ferry fiasco”, there was no clear indication that Sturgeon was going to quit.

Having been in parliament since the age of 29 and Scotland’s leader since 2014, Sturgeon is both the first female, and longest serving, first minister. She said she will stay on until her successor is elected. But that successor will inherit a government wrestling with several controversies and constitutional questions.

Sturgeon’s life’s mission of Scottish independence remains unfulfilled – and Scotland is deeply divided about “indyref2”. Recent polls have shown support for independence, but there are indications that support may be slipping away in light of the ongoing challenges facing the SNP-led Scottish government.

Three Conservative prime ministers (Theresa May, Boris Johnson and Rishi Sunak) have all refused to grant the Scottish parliament authority to hold another independence referendum, saying “now is not the time”. And the UK supreme court ruled in November 2022 that the Scottish parliament does not have the authority to hold a referendum on independence without Westminster’s permission.

This has led to a divide within the SNP about how to achieve independence. Sturgeon had announced that her “plan C” was to approach the next general election as a de facto referendum on independence.

This was met with mixed reactions from within the SNP, other nationalist movements, and the wider public. SNP MP Stewart McDonald was particularly vocal, highlighting this move as damaging for the independence movement. Alex Salmond’s Alba Party has also been very critical of the plan.

However dominant the SNP has been in Scottish politics over the last decade, it has never secured more than 50 per cent of the votes cast in Scotland at any UK general election. No party has achieved this level of support in Scotland since the 1950s, although the SNP came very close in its landslide UK general election of 2015.

Not winning 50 per cent of the vote at the next election would mean the SNP has difficult questions to answer about Plan C and the future of the independence discussion. Sturgeon’s resignation opens the door for a reconsideration of this approach.

And while Sturgeon emphasised that she is not leaving because of recent political pressures, there have been issues which have made her last few weeks particularly controversial – chiefly, the gender recognition reform bill, which the UK government blocked from receiving royal assent. This was the first time the UK government has intervened to prevent legislation passed by any devolved body from becoming law.

To members and supporters of the SNP, it is part of an ongoing intransigence and political interference from the UK government. The SNP, and others, consider this an assault on devolution itself. The implications for intergovernmental relationships within the UK are not fully clear, but the frosty relationship between Holyrood and Westminster became even colder.

However, for all the debate and vitriol surrounding the gender bill, it’s important to remember that it passed quite easily – 88 votes in support (drawn from all parties in the Scottish parliament) and only 33 against (drawn from two parties, the majority of Scottish Conservatives aligned with seven SNP MSPs). The latter was a rare occurrence: transgender issues, and the bill on gender recognition in particular, have highlighted a divide within the SNP – a party legendary for its internal discipline and focus.

The recent case of transgender prisoners within Scottish jails led to a very public debate, and the reversal of the Scottish Prison Service’s policy that allowed trans prisoners to be accommodated based on their self-declared gender. As the issue dominated headlines, polling showed declining support for Sturgeon and the SNP. Taken together, this leaves the next, yet to be chosen first minister with several issues (constitutional, legal and social) to deal with. Sturgeon’s departure has left a clouded political picture – with no immediate successor clear, and several constitutional and party issues unresolved.

Sturgeon’s no-nonsense, direct approach is a reason why she remains one of the most admired politicians in the UK. She has commanded a level of positive support that few others – especially the several Conservative prime ministers who have come and gone during her tenure – could match. Under her leadership, the SNP has dominated parliamentary elections in Scotland, whether for Holyrood or Westminster.

The SNP has been the party of government in Scotland for the past 15 years, and Sturgeon has been its face for the past eight. As she underlined in her resignation speech, she has come to represent these issues and debates in the public eye. By stepping down, she appears to hope this will allow for a more reasoned debate around the issues that Scotland faces, and the aim of independence that the SNP cherishes.

(The writer is Professor of Political Science, University of the West of Scotland. This article was published on www.theconversation.com)