THE tide is about to go out on the Scottish Tories - and what’s left behind won’t be pretty.

Ruth Davidson has been the party’s most successful leader under devolution by far.

The “working class, kicking-boxing lesbian’ of tabloid renown had a shaky few years after taking over from Annabel Goldie as a rookie MSP in 2011.

READ MORE: Ruth Davidson resigns as leader of the Scottish Conservatives 

But she found her voice during the independence referendum, then kept playing the Unionist card hard in election after election.

It was simple but effective.

The Tories leapfrogged Labour to become the main opposition at Holyrood, a feat once thought impossible.

READ MORE: Poll: Support for EU and holding a new Indyref rises 

Ms Davidson’s electoral record speaks for itself.

In the 2016 Scottish election she doubled her party’s MSPs from 15 to 31. A year later she more than doubled her councillors from 112 to 276.

And in the snap general election of 2017, the Scottish Tories went from one MP, the same taunting number they’d been stuck on since 2001, to 13.

Ms Davidson may credit the canny strategic planning of her friend David Mundell, the former Scottish Secretary, for much of the success on the ground.

But a huge amount of the party’s success was reliant on her energetic personality.

As she entered the pantheon of politicians known by just their first name, her face dominated every campaign leaflet, every manifesto, every conference.

It effectively became the Ruth party, with the Conservative brand gingerly underplayed.

She became the defender of the Union, the cross-over politician who could persuade Scots to vote for the party of Margaret Thatcher in order to stick it to Nicola Sturgeon

Her party’s entire approach to the 2021 Holyrood election was based on pitching her in a head-to-head contest with the SNP leader, asking voters to make her First Minister instead.

The Scottish Tories may not have been a fully-fledged personality cult, but they were getting awfully close.

Now, without that central, sustaining personality, the party faces a sharp reversal.

The SNP’s chances in the looming general election just got a whole lot rosier.

Ms Davidson’s resignation also adds to the growing instability around the Union.

In a second referendum campaign, she would have been the pivotal No spokesperson.

But the domestic and political pressures that have led to the end of her leadership would surely preclude that now.

Scottish Labour, who had been the main bulwark against independence, are in no fit state to do the heavy lifting.

The Scottish Tories also have the painful task of finding a replacement for Ms Davidson.

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The party’s other 30 MSPs all suffer from the same handicap. They look like Tories. She didn’t.

A leadership contest is likely to add to existing strains among MPs, MSPs and members.

Ms Davidson defeated Murdo Fraser in the leadership contest of 2011 thanks in large party to the support of the UK Tory establishment, who wanted to squash Mr Fraser’s plan for a breakaway Scottish party.

The establishment will doubtless want to interfere again by promoting a no-deal Brexiter, even though Scotland is now an avowedly Remain country.

There is a danger the contest will turn into a row between no-dealers and soft Brexiters, with the latter accusing the former of jeopardising the UK and helping the SNP.

Quietly relieved to be rid of Ms Davidson’s criticisms, Boris Johnson will probably prefer whichever candidate professes the greatest adoration for him.

The SNP will claim the Scottish Tories have lost the plot and any shred of credibility.

There may be a revival of Mr Fraser’s breakaway party idea.

Last month, when a poll showed majority support for independence, Ms Davidson sent the press cuttings to Mr Johnson to warn him off no-deal.

It is hard to imagine her successor doing the same.

With Ms Davidson out and a sycophant in, the Scottish Tories and the Union may soon be at their lowest ebb in years.