Ruth Davidson was never destined for greatness, her trajectory guided by an invisible hand of history like some politicians’ careers seem to be.

Everything she has achieved, she has achieved through hard graft and determination. Everything she has done, for good and for ill, has been shaped by a personal ethic that moulds her Toryism more than any volume of Burke or Hayek. She is a tactical thinker but an instinctual politician who leads from the gut.

Her gut now tells her it is time to bow out. After eight years as an MSP and leader of the Scottish Conservatives, Davidson is reported to be on the brink of resignation. Sources in her camp say the pressures of new motherhood have aggravated her disillusionment with the direction of her party at Westminster.

Baby Finn will turn one in October and 40-year-old Davidson intends to marry his other mother, her partner Jen Wilson. Those joyous pressures have been amplified by the unwelcome arrival, from Davidson’s perspective, of Boris Johnson in Downing Street. With him he has brought the prospect of no-deal Brexit and the prorogation of Parliament to that end. And so she must go.

Davidson reached the height of her political abilities only for her own party to take her legs out from under her. Now, she can ride off into the sunset and enjoy the rewards and trials of a normal family life. For her party, however, an ominous question mark had formed overhead. Is there life in the Scottish Conservatives after Ruth Davidson?

The query arises because Davidson was not another run-of-the-mill leader who put on a brave face and managed the party’s decline. She was transformative, resurrecting a political force long thought spent and reshaping Scottish politics in the process. She may not have been destined for greatness but she has made her name and earned her reputation as a political star.

To understand Ruth Davidson, you have to understand where she comes from. She was not born into privilege as so many prominent Tories are. There was no boarding school, no father with connections at Westminster or in the City. Nor is she a horny-handed daughter of toil reared on tales from the pit or the picket, like Labour giants of old.

Her upbringing was and her character is unsatisfyingly middle-class, lower or average depending on your perspective. Her dad Douglas is a former Partick Thistle player turned businessman and he and his wife Liz raised Davidson in Selkirk and later Fife. She attended Buckhaven High School, a bog-standard comprehensive which boasted the motto Perseverando — ‘persevering’.

That sums up Davidson well. She has always been persevering, whether in recovering from the broken back that ended her Army Reserve career, or going overnight from radio broadcaster to shop assistant after a sudden liquidation, or becoming the gay leader of a traditionalist party, or in defying her critics to restore the Scottish Conservatives after more than a generation in the wilderness. Adversity has never been far from her path but she has met it with tenacity and good humour.

Perseverance serves as a useful shorthand for Davidson’s brand of conservatism. She is well-read but not an intellectual Tory, her worldview formed by theory or philosophy. Her upbringing instilled in her the values of hard work, discipline, personal responsibility and self-starting ambition.

This, rather than any polling data or shifting political fashion, is why she is a blue-collar Conservative. She rejects the Left-wing characterisation of the Right as the Praetorian Guard of privilege and believes the ordered liberty of free markets and the rule of the law protects the interests of working- and middle-class people better than socialism.

There is a no-nonsense air to Davidson; she can be a very hard woman, though women in politics often have to be. This toughness is not an affectation — it emerges from her plainspoken politics. One of her political heroes is John Howard, the former Australian prime minister who was also a blue-collar Right-winger, also underestimated by his opponents and the commentariat, and whose harsh, gnarly persona helped him connect with working-class voters who had never voted for his party before.

Howard once floored Kim Beazley, a well-meaning Labor leader from a vaunted Australian political dynasty, with the charge that he ‘doesn’t have the ticker for it’. It was an Aussie-ism that cut through with ordinary voters who seldom paid attention to politics and made the debate one of personal character. Davidson sometimes cites it as one of her favourite political moments.

Personal grit has been in Davidson’s blood from the start but she has been hardened by struggle. The death of a teenage friend sent her into ‘a total tailspin’ and she began cutting her arms and stomach with shards of glass and knives. She punched walls, roiled with constant anger, and started to abuse alcohol. Her GP diagnosed her with depression but her prescribed medication only exacerbated her problems.

As an English literature student at Edinburgh University, she avoided sleep and lived a largely nocturnal life. The depression, she later reflected, ‘was like a smothering black blanket over my head, cutting out the sky… It was heavy, constricting, suffocating. It took away hope and energy and life.’

Last year, she became one of the first senior British politicians to speak openly about her battle with mental ill-health. She credits exercise, limited alcohol intake and her Christian faith with aiding her recovery.

Davidson was already a trailblazer as an openly gay woman, the first to lead a major political party in the UK. At first she strained to break free from the label ‘lesbian kickboxer’ but eventually she relaxed into her position as the face of the modern Tory Party and her newfound status as role model for gay youngsters coming to terms with their sexuality. In February 2015, she appeared in a groundbreaking party election broadcast which featured her partner Jen, updating the Conservative message on family values for the 21st century.

Last October, she gave birth to a son, Finn, with partner Jen by her side. In a testament to how much her example had changed Right-wing attitudes about personal morality, one of the first to congratulate the new mother was Arlene Foster, leader of the DUP.

That the head of Northern Ireland’s most God-fearing party would celebrate the birth of a child to the unmarried leader of the Scottish Tories and her Irish Catholic girlfriend would have been unthinkable before Davidson entered politics. Things change and Davidson deserves credit for helping to bring about changes like these.

The birth of Finn reinforced Davidson’s affinity for the NHS, another instinct that set her apart from some of her fellow Tories. She revealed her experience of the health service as an expectant mother, quipping: ‘There is a special feeling of wanting the earth to swallow you whole when you are led in a hospital gown to the room where an internal examination is going to take place by a nurse who decides to strike up a conversation with: “I saw you on the telly last night, talking about the NHS”.’

The NHS is in Davidson’s bones, quite literally. Aged five, she was run over by a truck outside the family home and rushed to hospital. She credits the doctors with saving her life and her legs. Years later, when she was serving as a signaller in 32 Signal Regiment of the Army Reserve, she broke her back in a training accident at Sandhurst. Once again, the NHS patched her up and ensured she would walk again.

As Davidson reflected in a speech at Glasgow University last year: ‘The NHS, the best expression of our country’s values that we have, is the foundation of this country’s social contract. And if we don’t ensure it is put it on a sustainable footing over the coming years, we won’t just suffer as patients – we will see faith in that contract collapse completely.’

This is who Davidson is as a politician and a person but it is not what she is best known for. The Scottish Conservatives are losing a leader but the Union is also losing its hardiest, most energetic champion. Davidson came into her own as a political leader during the 2014 independence referendum. This 5’ 5’’ firecracker exploded onto the national scene, going toe-to-toe with the Nationalists and matching their passion for independence with a heartfelt belief in the Union.

Davidson is not a nationalist but she understands how they think because she is a patriot. Where they see Scotland as a victim held back by Westminster, she sees the UK as a sacred trust between nations and people that at its best can be a force for good at home and overseas. Yet again we arrive at another Davidson peculiarity: she is a Tory optimist.

Her efforts in 2014 contributed to the defeat of nationalism and when the SNP refused to accept the outcome, Davidson stepped up her campaign and in the process became a largely one-issue politician. Labour having abandoned its pro-Union stance in vain hope of winning back voters who had switched to the SNP, Davidson was free to reinvent herself and her party as the guardians of the Union. This allowed her to appeal to those ordinarily hostile to the Tories but who grasped the menace of nationalism.

Davidson embraced her new role as Boudica in a power suit and basked in the confidence it gave her. During one Holyrood debate on Indyref2, Nicola Sturgeon attempted to intervene on the Tory chief, who snapped ‘sit down’ at her opposite number. The debating chamber immediately emptied of air and sound as a stunned Sturgeon resumed her seat. The rules of the game had changed.

It was about more than rhetoric, though. Davidson took a defibrillator to the Scottish Conservatives and returned the party to rude health in the face of much disdainful blather from the commentariat. The 2016 Holyrood election saw the Tories double their representation in the Scottish Parliament from 15 to 31, supplanting Labour as the main opposition to the SNP.

Even then, her detractors denied the evidence in front of them and were again proved wrong in the following year’s General Election. A month before polling day, one of Davidson’s more self-assured critics complained to readers of a London-based magazine that the media was ‘talking up a Tory surge in Scotland’ when, he averred, ‘the Conservatives will increase their seats tally from one to four with a fair wind. Maybe seven if 8 June 2017 is a very good night’. One month later, the voters sent 13 Scottish Tory MPs to Westminster.

In politics, the efforts of many are often ascribed to the toil of one figurehead man or woman. In the case of the Scottish Tory revival, however, Davidson did most of the heavy-lifting and transformed her party as much by the force of her personality and inner determination as by the quality of the candidates it now fielded.

What Davidson could not control was the divergent political ambitions of others. The Right of the Tory Party had made the UK’s withdrawal from the European Union its crusade and when it convinced a narrow majority of the country in 2016’s referendum, Davidson was thrown into conflict with her party. Scotland overwhelmingly voted Remain and Brexit would be used by the SNP to agitate for a second plebiscite on separation. Davidson would have to ride two horses: loyalty to her party and loyalty to her political nous and personal conscience.

The election of Boris Johnson as leader of the Conservatives snapped the tether fastening those two beasts together. Davidson could either be a good Tory, or a successful Scottish Tory; a democrat willing to accept an orderly Brexit but not a chaotic no deal, or a hypocrite conceding more ground by the day to a wing of her party for which she feels no love or political fidelity.

In the end, her Westminster colleagues dragged her to a line in the sand she could not cross. A woman once touted as a possible successor to David Cameron has been undone by the same forces that did for him. The Conservatives don’t just knife leaders, now they knife potential leaders too.

What will become of the Scottish Tories now? They face seeing all the gains Davidson made evaporate as Nicola Sturgeon is spared her toughest opponent and the Union its doughtiest defender. In the coming days and weeks her would-be successors will put forward their credentials but all will be judged against the metric of the woman who went before them and all will be found wanting.

Ruth Davidson is the Scottish Conservatives and a new leader will have to fight to preserve her legacy while stamping their own imprimatur on the party, all the while managing the political fall-out of a no-deal Brexit and fending off fresh attempts by the SNP to force a second independence referendum. There may be only one person in the Scottish Tories equal to that challenge and she is heading for the exit.

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Originally published in the Scottish Daily Mail. Letters: scotletters@dailymail.co.uk . Contact Stephen at stephen.daisley@dailymail.co.uk .