Illustration by Ralph Steadman

During Scotland’s independence referendum, George Robertson, the former Labour defence secretary and Hamilton South MP, told a joke about his Scottish National Party opponents. “The Italian Mafia might make you an offer you can’t refuse,” Robertson sneered. “But the nationalists will make you an offer you can’t understand.”

As the dust from the 18 September poll begins to settle, Scotland’s Yes campaigners are trying to work out what went wrong. The dominant theory is that the SNP mangled its pitch. On the one hand, Alex Salmond said independence would transform the Scottish economy. On the other, he conceded that monetary union would restrict the country’s fiscal autonomy. Salmond regularly hinted at post-independence increases in public expenditure but ruled out tax rises to fund them. He said Scotland could borrow more to end austerity but dismissed claims that this would increase the deficit.

Nicola Sturgeon’s appointment as SNP leader – to be confirmed, unopposed, at the party’s annual conference, which starts in Perth on 14 November – will reveal whether these inconsistencies are specific to Salmond’s vision or an embedded feature of nationalist politics. The feeling among activists matches the media consensus: Sturgeon will give the SNP a more coherent social-democratic profile. But quite how radical Sturgeon will be when she takes charge of the Scottish government – a government that still commands a working majority at Holyrood – is less clear. The incoming first minister has, after all, served loyally as Salmond’s deputy for more than a decade.

Nicola Sturgeon, 44, was raised just outside Irvine, a modest new town in industrial North Ayrshire, and joined the SNP as a 16-year-old in 1987. She worked on her first campaign that year, leafleting for the SNP’s general election candidate in Cunninghame South, Kay Ullrich, a nationalist veteran who signed Sturgeon up to the party in her front room. “My team was just about to set off when there was a knock at the door,” Ullrich tells me. “‘Hello, Mrs Ullrich, my name’s Nicola Sturgeon. Can I help with your campaign?’ . . . She had ambition, that was obvious. But, from day one, this lassie also had a social conscience beyond her years.”

Neither of Sturgeon’s parents was very political; her father, Robin, was an engineer, while her mother, Joan, now a high-ranking SNP councillor, stayed at home. Even so, Sturgeon’s social awareness was forged early on, as she saw the impact of ­rising local unemployment. “In the 1980s, in this part of Scotland, heavy industry was crumbling all around us,” Ullrich says. “We were losing big firms like Monsanto and the Glengarnock steelworks. And Nicola went to a working-class school. She saw her classmates struggle to get jobs.”

Sturgeon studied law at the University of Glasgow and then completed her legal diploma and traineeship. In 1992, aged 21, she stood for the SNP in Glasgow Shettleston but won less than a fifth of the overall vote as Labour prevailed. Five years later, identified by the party hierarchy as a future star, Sturgeon was picked to fight another Labour seat – Govan, the scene of iconic nationalist by-election victories in the 1970s and 1980s – but lost again, this time by a much smaller margin.

Sturgeon’s efforts were finally rewarded in 1999, when she was elected on the Glasgow regional list to serve in the newly devolved Scottish Parliament. Her discipline impressed senior colleagues and she was quickly handed a series of briefs – education, health and then justice – on the SNP’s opposition front bench. In 2004, John Swinney ended his short, fraught tenure as SNP leader and Sturgeon, only in her early thirties, made a bid for the vacancy. “I offer a fresh start, a new generation of leadership,” she said at the time. “We need to re-establish this party as the party of social democracy. That is at the heart of what I believe.”

But her plans changed when Alex Salmond announced his intention to return to Holyrood. Sturgeon withdrew her candidacy and ran instead as his deputy. Since then, their partnership has dominated Scottish political life, with Sturgeon’s steady, premeditated approach balancing Salmond’s more improvisational style. Despite reports that Sturgeon was unhappy with the SNP’s decision, in 2012, to drop its long-standing opposition to independent Scottish membership of Nato, there have been no public disagreements or disputes. “Our relationship is unique in modern politics,” Sturgeon has said. “Alec and I actually like each other.” (Salmond is known to his good friends as “Alec”.)

Since 2007, when the SNP came to power in Scotland, Sturgeon has developed a reputation for administrative competence. As Scottish health minister – a role she twinned with her duties as deputy first minister – she won praise for her handling of the swine flu crisis. Barring an incident in 2010, when she lobbied a court on behalf of a fraudster constituent, there have been no career-threatening controversies. ­Unlike Salmond, who can be belligerent and scatters his conversation with gallus jibes against opponents, Sturgeon is liked and respected by rivals, as well as by civil servants.

“Over the years, I’ve always found Nicola to be one of the people in the SNP who’s very straight-up-and-down,” Patrick Harvie, the leader of the Scottish Green Party, tells me. “If we could find common ground, we’d find it. If we couldn’t, we’d leave it. My dealings with [Salmond] didn’t always end that way . . . [Sturgeon] approaches her responsibilities with a real seriousness.”

“Serious” is a word that is often used about Sturgeon. “Guarded” is another. She is distrustful of journalists, possibly ­because she has been on the receiving end of some unpleasant treatment by Scotland’s overwhelmingly male press corps. But she tends to keep her non-party allies at a careful distance, too. One high-profile Yes campaigner describes her as a “bunker politician”. “She has an intensely loyal team,” he says. “Hardly anything leaks out.”

Sturgeon has built a strong base in Glasgow. The once impenetrable Labour heartland was one of only four areas across Scotland to back independence. At the 2011 devolved elections, she won Glasgow Southside, a multi-ethnic, working-class constituency, with more than 50 per cent of the votes, compared with the 35 per cent for her Labour opponent, Stephen Curran.

“She’s been campaigning here for two decades,” says Natalie McGarry, a Glasgow SNP activist who is close to Sturgeon. “Salmond’s power base is up in the north-east, which is very different. Nicola [sees] poverty and unemployment every time she walks through the city . . . Glasgow is important to her political identity.”

Yet Sturgeon has her critics. “She is a more rounded politician than she was a decade ago,” one senior Scottish Labour source tells me. “The money on her image and training has been well spent. But there’s a core to her that remains combustive and harsh . . . She is the single most partisan politician in Scotland, which makes her – perhaps ironically – particularly badly suited to the new politics she has done so much to create.”

Sturgeon’s friends, however, insist that there is no major difference between her public and private personas. “She’s funnier [in private], maybe. Very quick-witted,” one tells me. “But what you see with Nicola is pretty much what you get.”

Other than a well-publicised obsession with the Danish TV drama Borgen – she and the Borgen actress Sidse Babett Knudsen met in Edinburgh a few years ago and appeared together on an STV question-and-answer programme – Sturgeon has little time for anything outside politics. In 2010, she married Peter Murrell, the SNP’s influential chief executive and party fixer. They don’t have children.

During the referendum, Sturgeon thrived in the media debates and on the campaign trail. If she wasn’t ready to replace Salmond before September, she is now. And it’s difficult to imagine a more favourable set of circumstances for her to inherit. The SNP’s membership currently stands at 83,000, up from 25,000 two months ago. The nationalists lead in both the Westminster and Holy­rood polls. Scottish Labour is in crisis. But the question remains: what, precisely, are her plans for Scotland’s future?

I meet Sturgeon on 30 October in her Holyrood office, a compact room on the fourth floor of the main parliament building. It is the morning after she launched her Obama-style speaking tour of Scotland – a month-long, six-venue circuit – at the Corn Exchange on the outskirts of Edinburgh. Sturgeon spoke to her supporters for 90 minutes. If she is tired, it doesn’t show.

I ask first about her idea of imposing a Celtic lock on any future UK withdrawal from the EU. England should not be able to drag Britain out of Europe without the consent of voters in Scotland, Wales or Northern Ireland, she argues. It’s an audacious move, typical of the modern SNP, and one that has enraged Eurosceptic opinion south of the border.

“The UK is not a unitary state,” Sturgeon says. “It is a multinational state. It was described during the referendum campaign by the Westminster parties as a family of nations, a partnership of equals.

“Therefore, if the UK was to exit the European Union, which I’m against, then it seems to me fair, right and democratic that that should require not just a vote across the whole of the UK, but a vote in each of the four component parts of the UK. Otherwise, you raise the prospect of Scotland voting to stay in while a UK-wide vote would be to come out . . . That strikes me as fundamentally and profoundly wrong.”

Sturgeon denies the proposal is an attempt to engineer a second independence referendum. “This is a genuine, sincere proposition that would protect Scotland, Wales and Northern Ireland from being taken out of Europe against their will. When you’re in a multinational state, there are things you have to accept. If it’s the case that the biggest partner can always outvote the smaller partners, then what’s the worth of a Scottish vote in an in/out EU referendum? So it’s not positioning but it is a test of what the Westminster ­parties said the UK was during the referendum campaign.”

Sturgeon’s immediate task is to refashion the SNP for the post-referendum landscape. Although she remains staunchly in favour of independence, she says she will co-­operate fully with the Smith Commission, which is convening cross-party talks to agree new powers for the Scottish Parliament. Sturgeon acknowledges that she isn’t going to get everything she wants from the commission but is confident of a compromise. She is similarly pragmatic when it comes to the 2015 elections. Sturgeon appears open to the idea of running a slate of pro-independence (or, more likely, home rule) candidates, from a range of different parties and campaigning groups, in constituencies across Scotland next year – a concept popular with the nationalist grass roots.

“I’m keen on the idea of exploring all options that will strengthen Scotland’s voice and position in the election and in the next Westminster parliament,” she says. “I haven’t ruled anything in and I haven’t ruled anything out.”

As if to emphasise the point, she describes working with Patrick Harvie during the referendum as “a really refreshing experience” and praises the left-wing Radical Independence Campaign (RIC). “I don’t agree with everything Radical Independence put forward but their contribution to the referendum both in terms of ideas and in a hard, organisational sense – doors knocked and miles covered – was [hugely positive]. They did a huge amount of work in my own constituency and in areas like the Gorbals, which voted Yes overwhelmingly. Organisations like [RIC] were part of the strength of the Yes movement.”

Sturgeon speaks in confident, complete sentences. She has a strong sense of her own authority. If she doesn’t want to answer a question, she says so directly and moves on. Given her background, it’s entirely possible she might have joined the Labour Party in 1987. But her opposition to nuclear weapons, coupled with her desire to permanently rid Scotland of Tory governments, pushed her towards the SNP. Of the current Scottish Labour Party, she is, unsurprisingly, scathing: “They have never reconciled themselves to devolution. They have lost their way politically and in terms of where they stand ideologically. They don’t seem to know what their purpose is. They’ve lost any sense of identity,” she says.

When I ask if the SNP is frightened of the former secretary of state for Scotland Jim Murphy, the frontrunner to replace Johann Lamont as the Scottish Labour leader, she laughs: “Not in the slightest. Not at all, actually. On the contrary.”

But what of Sturgeon’s own values? When she describes herself as a social democrat, what does she mean? “I’m a child of the Thatcher years. I came into politics because of my desire for social justice and greater equality. My background, where I grew up, all of that has conditioned my perspective. But I understand that you can’t do anything unless you have an economy that creates the wealth and generates the revenue to fund and pay for [reform]. So, for me, social democracy is understanding that you need a strong, sustainable, balanced economy but for the purpose of creating greater social justice.”

When I press for more detail, Sturgeon says she is a “great believer” in “as collaborative a model of industrial relations as possible” and that she would like to “equalise the minimum wage with the living wage” – a more ambitious position than the SNP’s current pledge to increase the minimum wage in line with the rate of inflation.

“There’s no doubt in my mind that we’ve got to recharge our whole approach to inequality,” Sturgeon says. “At the moment, it’s going in the wrong direction, very largely because of the Westminster assault on welfare . . . But [tackling inequality] is one of the big preoccupations I’ll take into the job [of first minister] with me.”

Intriguingly, when I raise the SNP’s controversial commitment to lowering corporation tax – something that causes much disquiet on the nationalist left – she refers to the policy in the past tense.

“The point of the corporation tax proposal was to stimulate economic activity. I don’t have power over corporation tax right now. If I did have power over corporation tax, I think there are a number of different things you could do with it . . . But I will set out a policy programme in the fullness of time and it will come from the perspective of what I’ve just described: having a strong economy but one that translates into greater equality.”

Sturgeon is a working-class woman in a profession dominated by middle-class men. The actress Elaine C Smith, a friend and prominent independence supporter, says Sturgeon has had to “work harder and be better” than her male colleagues. “The shift needed in Scotland’s political landscape for Scots to accept a woman leader has been massive,” Smith says. “It was unthinkable in the 1980s. But it’s great it’s happening now, and that it’s happening with Nicola.”

Sturgeon tells me: “I’m privileged to be in the position of, hopefully, being the first woman first minister. I hope very much it sends a positive message to women and to girls that, if you work hard enough, if you’re good enough, there are no artificial glass ceilings.

“But I don’t want people to think that, because we have a woman first minster, we don’t have a problem with gender equality. We had a female prime minister at the UK level and gender equality didn’t progress at all . . . I argued in favour of positive action schemes [within the SNP] and lost. I’d be prepared to argue for them again in certain circumstances.”

Our conversation turns to Glasgow. Sturgeon’s election as SNP leader will complete the party’s shift away from its traditional Perthshire and east coast heartlands and towards urban Scotland and the central belt. Post-referendum, Scotland’s largest, poorest, brashest city has become the focal point of the new constitutional radicalism.

“Glasgow is my personal and political home,” Sturgeon says. “It’s the city I represent in parliament. It is hugely important to me. I’m not a native Glaswegian, although I’ve lived there longer than I haven’t.

“I’m really proud Glasgow voted Yes. I’d rather the country had voted Yes but it’s significant and positive that Glasgow voted Yes. I was there on polling day . . . which probably explains why I thought we were going to win . . . It was the most uplifting and emotional day of my life.”

A few hours after I leave Sturgeon’s office, an extraordinary new poll of Scots’ 2015 voting intentions puts the SNP on 52 per cent – 29 points ahead of Labour. If this were translated into seats next May, it would wipe out all but four of Labour’s Scottish constituencies, while the SNP’s tally at the Commons would rise from six to 54. A second poll shows that a majority of Scottish voters back independence.

Sturgeon is a deeply cautious politician, a calculated decision-maker. She does not commit to anything lightly. But there is a momentum gathering behind her that is powerful enough to change Scottish – and British – politics for ever. Her biggest challenge may yet be meeting the ever-­heightening expectations of her supporters. The good news for them is that Sturgeon seems ready – just about – to move beyond some of the old Salmond-era ambiguities.

Jamie Maxwell is a regular NS contributor and blogger