Frustration at her powerlessness to change the country prompted Scottish Tory leader Ruth Davidson to quit her well-paid, four-days-a-week job as a popular drivetime radio presenter in 2009 in order to stand for Holyrood. The irony of Davidson, now 37, nailing her colours to the mast of the sinking Conservative ship in Scotland so as to grab hold of the levers of change isn’t lost on her. “My mother was horrified, as you can imagine,” she admits, sipping on a glass of water in a fashionable Edinburgh bar near Holyrood.

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The Scottish Conservative party’s results at the 2015 general election – the first under Davidson – were unlikely to have offered her mother much succour. The party suffered its worst ever UK return, with just 14.9% voting Conservative; the brand having been on the slide ever since Tories north of the border failed to differentiate themselves from Thatcherism in the 1980s.

But these are extraordinary times in Scottish politics and, to a great extent as a result of the slow-motion implosion of the Labour party, Davidson’s mum could be in for a welcome surprise. “Tories ‘could form official opposition at Holyrood’,” screamed a recent headline in the Scotsman.

The latest polling ahead of May’s Holyrood election has the SNP on 50%, Labour on 21% and the Conservatives on 18%. There is only one winner here, but the contest for that second spot is tight and Davidson’s pitch is simple: if you want a strong leader to hold the rampant SNP to account then she will do it. And, she will take any opportunity to remind those who voted No in the 2014 referendum that she is utterly sound on independence.

While the Labour leader, Kezia Dugdale (exposed as having applied for work experience with the SNP in the Scottish parliament in 2003), has suggested she could support independence if the UK voted to leave the EU (a confession she swiftly retracted), Davidson says she doesn’t believe there can be any excuse for another poll on that subject. “I struggle to see how even the SNP with their political gymnastics can argue that it is so important for Scotland’s interests that we stay part of a wider union [the EU] to which we export 16% of our goods and services but that we must leave a union [the United Kingdom] to which we export 64% of our goods and services,” she says.

Davidson adds: “We are going into the election being really upfront with people about what the relationship is. If you vote for me I will do a very specific job for you. And that job is to hold the SNP to account, fight against any attempt at a second independence referendum and make them concentrate on the things that matter to you.”

She stalls a little when asked about the impact of the Panama Papers and the coverage of David Cameron’s tax affairs, calling over her press adviser to “listen to this stuff” just in case the line of questioning becomes awkward.

After pausing for a bit she says: “I think the electorate in Scotland is pretty sophisticated so they know what they are voting for. This is not a David Cameron versus Jeremy Corbyn election, because neither is on the ballot paper. It [the Panama Papers revelation] is a noise off, but in terms of having a material impact on the outcome of this campaign, I don’t think so.”

But, for all that moment of hesitancy perhaps suggests her continued concern about the toxicity of the Tory name, there is a confidence and buoyancy to the Conservative leader in Scotland. She is a dab hand at photo opportunities, aware that much of her job is to keep her party on the map. Not many frontline politicians would throw a friendly V-sign at their spin doctor when a camera is around.

And, with the knowledge that she needs to differentiate herself from the coterie of public school boys at the top of the party in London, Davidson feels free to write off the leadership ambitions of two of the big hitters in the political cabinet of which she is a member (“I actually think it will get past both Boris [Johnson] and George Osborne”). She is backing the new work and pension secretary, Stephen Crabb, for the position.

Facebook Twitter Pinterest Kezia Dugdale, Scottish Labour’s leader, has taken the party to the left. Photograph: Murdo Macleod/The Observer

When asked how Corbyn’s leadership is being received in Scotland, she responds with a prolonged belly laugh.

“I don’t think Jeremy Corbyn’s leadership is an unalloyed success for Scottish Labour,” she adds after composing herself.

Labour insiders put it rather more succinctly. “We are fucked,” confided one former Labour official. “Utterly fucked, to use a technical term,” repeated a former Scottish Labour MP.

It has been a devastating few years for Labour. Ousted by the SNP as the giants on the scene, the polls now suggest their numbers at Holyrood will be at least halved from the 38 currently held under the mixed proportional representation system, with some predicting the party could lose every one of its 16 constituency seats. Under Holyrood’s mixed proportional representation system, 56 of the 129 seats are elected via regional lists. The party, fresh from a general election drubbing where it was left with just one MP in Scotland, will instead rely on voters using their second vote to give it representation.

With such a rout looming, there is a battle going on behind the scenes to apportion blame. Sources close to the Labour leadership in London point out that Corbyn has generally stayed away from Scotland, allowing Dugdale to make her own choices, and mistakes. Her neck appears to be on the line.

Those supportive of the Scottish Labour leader, or at least sympathetic to her position, point out that Dugdale is being stridently anti-austerity in her message, tacking to the left of the SNP, as presumably Corbyn would want it.

Former MP Thomas Docherty, one of the 40 Labour MPs to lose their seat at the general election, is standing for the Scottish parliament in Mid Scotland and Fife and describes the Scottish Labour party’s manifesto – support for unilateral nuclear disarmament, an increase on the Scottish rate of income tax and an increase in spending – as “unambiguously socialist”.

“Jeremy’s people have told us throughout that Jeremy was going to improve our circumstances in Scotland,” he says. “At the 2011 election we had 26% of the vote, so let’s see how it goes.”

But he believes it is not only Labour who should worry about what might be coming down the line, given that in his opinion the Conservatives will never get above 20% in Scotland.

Drinking coffee in the lounge of the Queensferry Hotel, with views of the Forth bridge and the Rosyth dry docks, where the Royal Navy’s two new aircraft carriers are being constructed, Docherty says the greatest danger in the party’s potential defenestration might be in breaking apart the organisational capacity that delivered a No to independence in 2014. “It’s why the nationalists put out the story about Kezia applying to do work experience with the SNP,” he says. “They know that in order to win a referendum they need to destroy the Labour party. There is no way the Conservatives and Liberals could deliver the vote.”

Twenty-five miles north, that isn’t a consideration for Dean Lockhart, of course, the Tory candidate in Stirling. . He has a chance of stealing a seat on the regional list here and the former corporate lawyer is determined to take it. As a boy, when he was growing up on a council estate, Lockhart would walk down Keir Hardie Road, turning into Wilson Street and on to Clem Attlee Gardens to get home from school, but he isn’t sentimental about helping to kill off the old giant.

Striding out in the middle-class suburb of Torbrex, in Stirling, in his luminous blue wind-cheater (“People see it and they are reminded that we are back”), Lockhart knocks on the key battleground doorsteps – those who voted No in the referendum; who are more advanced in years; and who are dismayed by the SNP’s seizure of power. “You don’t want a second referendum, and we will fight it,” he tells the voters. “Ruth Davidson is a strong leader isn’t she?” he asks.

This is Davidson’s chance to break the “soft left consensus in Scotland” and expose the lie of a left-wing “Scottish exceptionalism”, she admits. “A lot of people have left Labour in recent years. A lot of those who are left are older, core voters who have worked hard all their lives, done the right things, saved a bit of money, bought their council house, for example,” she says. “They look at the crackpot economic policies espoused by Corbyn and they want to run a mile. It is not the Labour party they know. It is not a Labour party they want to be a member of and it doesn’t speak to them, their children or their grandchildren.”

• This article was amended on 17 April 2016.