Image copyright Getty Images Image caption Ruth Davidson's broad appeal was based on not looking like a typical Conservative

Ruth Davidson's unique selling point has always been that she doesn't look or sound like a Tory so she could persuade people who would never previously have considered voting Conservative to at least give them a hearing.

When the Tories fight election campaigns in Scotland they don't do it under the name of the "Scottish Conservative Party". They do it as "Ruth Davidson's Party". It's her picture that looms large on campaign leaflets. Any mention of being Conservatives is consigned to the small type.

That's been Ruth Davidson's great success. Detoxifying the Tory brand in Scotland. She says she is proud that Conservatives can now knock on doors in Scotland without always having to apologise for being Tories. The question now is what happens to that brand without her unique personal appeal.

Under her leadership the party won 13 seats in the last general election. Up from having just one MP. That success was crucial to keeping Theresa May in Downing Street and the Tories in power.

Image copyright Getty Images Image caption The Scottish Tories campaigned as Ruth Davidson's party

Will they be able to hold all those seats under a different, less vibrant leader?

Another election may well be imminent so it is an important question. It is possible we may all be at the polls again before the Scottish Tories have even had time to elect a new leader.

Force of personality is not the only thing that has propelled the Tories into second place in Scottish politics.

Ms Davidson was helped enormously by the fact that the dominant issue in Scottish politics throughout her eight years as leader has been Scottish independence.

As a fierce advocate of staying in the UK she attracted unionist votes from other parties and became the standard bearer for keeping the Kingdom United.

That was her number one policy and as long as she was fighting against another Scottish referendum she didn't have to spend too much time defending austerity policies or tax cuts introduced by her party at Westminster.

Image copyright Getty Images

Ms Davidson may have moved to the backbenches but the arguments about independence are still front and centre in Scotland.

So does her departure make an independent Scotland more likely?

Since Boris Johnson became PM we saw an opinion poll that suggested more Scots might now vote to leave the UK than to stay.

I realise that anecdotes are not evidence but I am struck by how frequently I hear people all over the country saying that they have now changed their minds and would vote for independence if there was another referendum.

Without the dynamism and charisma of Ruth Davidson leading the campaign for the UK where will a future "Better Together" campaign get its energy from now the Scottish Labour Party is a mere shadow of its former self?

Her spokesman today would not be drawn on whether she might be persuaded to play a leading role in a future referendum campaign.