IT’S one of my favourite political quotations: “Even victors are by victories undone.” The line comes from a 1699 poem by John Dryden, memorialising his cousin’s life in politics. I like the thought, because it neatly captures a hardy perennial of human experience – that today’s win has a long history of sowing the seeds of tomorrow’s defeat.

What looks like an unmitigated triumph tonight may seem rather different when the dawn pulls itself up. This might suggest a melancholy outlook on political life, but I’d explain it differently. When everyone around you is cheering – or in their dumps, having taken a drubbing – it reminds you that you never really know what tomorrow holds. The silver lining in the cloud may be hard to see, but so is the summer lightning crashing out of the blue.

Recent electoral history furnishes a slew of examples of victors being undone by – or at least taking painful, unforeseen knocks from – their victories. The 2010 hung parliament led the LibDems into government and flensed them of 49 seats at the next election. David Cameron’s surprise majority in 2015 paved the way for the Brexit referendum, and the end of his own political career.

In Scotland, I’ll never forget bumping into Margaret Curran outside Pacific Quay as the results rolled in after September 14, 2014. Then shadow secretary of state for Scotland and MP for Glasgow East, Curran was a picture of elation. She even allowed herself a strange little jig on the spot – which, considering what was coming Labour’s way within a few months, now seems more like a danse macabre for her party.

The SNP’s surprise majority paved the way for the first independence referendum, but also the Offensive Behaviour at Football Act. The party’s surge in the 2015 General Election was remarkable, but the 56-seat win was a high-water mark from which the tide could only recede. In the wrong light, 2015’s historic over-performance made the party’s solid turn in the snap Westminster poll two years later look like a setback.

This summer, it seems like it’s the leader of the Scottish Tories who is experiencing one indispensable rule of political gravity: what goes up, must come down. It hasn’t been entirely plain sailing for the Scottish Tory leader since her elevation in 2011. Although largely forgotten after a half decade of fawning, soft-focus coverage, Ruth Davidson’s early appearances as Tory leader in Holyrood attracted critical notices from much of the Scottish media. These teething troubles weren’t surprising. Even with considerable experience as a BBC broadcaster behind her, frontbench politics was a new domain for the 32-year-old. But since Davidson found her parliamentary feet – like it, love it, loathe it – she’s been on the up and up.

Emerging personally and politically strengthened from the independence referendum, achieving unprecedented national recognition for a Scottish Tory leader, securing the election of 16 new Tory MSPs in the 2016 election, supplanting Labour as the biggest opposition grouping, and snaring 12 new seats in the surprise Westminster election of 2017 ... in purely electoral political terms, this is an undeniable tally of gains.

The Tories may not have come close to winning any of these elections, but the press are suckers for a new story.

But she picked up some important vulnerabilities along the way. When Davidson won the Edinburgh Central constituency in 2016 with a majority of 610, it seemed like victory in every light. A constituency snatched from the SNP; a personal victory for the Scottish Tory leader in an unanticipated, urban seats. But – nag, nag, nag – if you dug into the numbers and thought about tomorrow rather than today, it was one of those victories which forged a chain for the victor.

Remember the backstory. Davidson was first elected to Holyrood on the Glasgow regional list, but flitted east to the Lothian list in 2015. She might have been a comfortably free-floating regional member, secure at the top of her party’s list, impossible to dislodge without a crashing fall in the Tory vote. With the Edinburgh Central win, however, Ruth Davidson finds herself personally exposed.

In exchange for the fillip of having won a constituency seat, Davidson was now encumbered with defending it. And if you were the leader of the Conservative Party in Scotland, keen to avoid personal embarrassments, you wouldn’t choose to be elected in Edinburgh Central.

In the first-past-the-post race in 2016, Davidson came out on top with 29% of ballots cast. Her 10,399 vote tally compared to 9789 for the SNP candidate, 7500 for Scottish Labour and 4644 for the Scottish Greens who – unusually – decided to run in the constituency.

If the anti-Tory vote can be marshalled by a compelling candidate, these are numbers which could topple Davidson. The bungee cord of the regional list will save her – but there’s no escaping the political whiplash. It is hard to look like Hannibal when the voters in your own constituency have rejected you. As I say, even victors are by victories undone.

I’m sure there have been rough days, but thus far, Davidson has enjoyed a charmed political existence. She arrived in the right place, at the right time, with the right set of communication skills to exploit the moment. She may have no evident policy commitments, almost no core convictions, no plans about how to govern Scotland and no shame about reversing those few policies she has publicly committed herself to, but these are vices few political hacks will hold against you. Not if you talk a good game.

The question is now: how will she cope with a political career sliding – for the first time – on to a downhill gradient? On the evidence of her recent ashen-faced performances, not well. The confrontation between “Ruth Davidson for First Minister” and reality was always likely to knock the Tory leader into a descending orbit, but the context for her next Holyrood run looks increasingly difficult.

She now faces the prospect of daily questioning about whether she agrees with the Prime Minister’s latest gaffe or half-cocked policy announcement. Brexit is unresolved and sliding towards the real possibility of a No Deal outcome she says she opposes, but can do nothing to stop.

Obliterating the cosy media spin, the recent leadership race has revealed her as without influence in the UK party. Her endorsement was like the black spot, and she unnecessarily and unwisely distributed it among a succession of doomed candidates. When they stir from the foetal position to yelp “no indyref2” at the uncaring stars, the Scottish Tories continue to push the idea they’re “Team Ruth”. Recent experience has given the lie to the idea the Scottish Tory group in Westminster are in any significant sense “her MPs”. The Tory MPs aren’t a coherent bloc with distinctive interests, but have proven to be a loose confederation of warring tribes, pursuing their own ambitions, equally inclined to look to London for their political leadership as Edinburgh.

Personally and politically, Ruth Davidson looks increasingly like a politician who has had it. And if and when she calls it a day, what will she leave behind her? What’s Team Ruth without Ruth? What does the Ruth Davidson for a Strong Opposition Party look like without its titular head? I’d suggest they look like what they are, when the mask falls away: plain, unmodernised, old-fashioned Tories. The party of Alister Jack. The political wing of Scotland’s private schools. The landlord’s and landowner’s friend. Uncritical proponents of mass incarceration, however much it costs, and however little good it achieves. A party for people prepared to put up with any indignity at the hands of the UK Government, so long as the humiliation comes fully Union-Jack branded.

And that’s all there is. A union preserved for a time. A triumph of personal PR. The husk of an unthinking party, tactically soulless, largely unreformed, surviving on one slogan, boosted by a few seats but exerting no real influence on anything that matters. All political careers, classically, end in failure. But Ruth Davidson’s now risks winking out – not with a bang, but a whimper.