William Cowan Rennie is a Scottish politician who has been the Leader of the Scottish Liberal Democrats since May 2011. After college, Rennie spent most of his early career as a Liberal Democrat election campaigner and official before working as a public relations consultant in the private sector.
But she added that "much had changed" both politically and personally, which had led her to tender her resignation.
The 40-year-old, who will continue as the MSP for Edinburgh Central, tweeted her resignation statement shortly before addressing the media at an event in Edinburgh on Thursday morning.
Conservative sources insisted that her decision to leave The Post had been building for several months, and was not a direct result of Mr Johnson announcing that he would suspend parliament for several weeks ahead of the Brexit deadline on 31 October.
Ms Davidson has been widely credited with turning around The Fortunes of the Tories in Scotland, But backed opponents of Mr Johnson in the Conservative leadership race and has said she could not support a no-deal Brexit.
Mr Johnson paid tribute to Ms Davidson's "incredible leadership", which he said had been "instrumental in The Revival of our electoral fortunes in Scotland".
The Prime Minister added: "She should take immeasurable pride in the pivotal role she played during the Scottish independence referendum campaign, where her passionate support for our Union was crucial to the result".
Her deputy, Jackson Carlaw , will become acting leader - a role he filled during Ms Davidson's maternity leave - until a permanent successor is chosen.
Ms Davidson backed Remain ahead of the EU referendum and famously clashed with Mr Johnson in a BBC TV debate at Wembley ahead of the vote - When she accused the Leave side of telling "untruths".'Fills me with dread'
She Said she had never sought to hide the "conflict" she felt over Brexit, But had attempted to "chart a course for our party which recognises and respects the referendum result, while seeking to maximise opportunities and mitigate risks for key Scottish businesses and sectors".
"Having led our party through seven national elections and two referenda, I know the efforts, hours and travel required to fight such campaigns successfully.
"I have to be honest that where the idea of Getting On The Road to fight two elections in 20 months would once have fired me up, The Threat of spending hundreds of hours away from my home and family now fills me with dread. That is no way to lead. "
She also said she feared her focus On Being a "good leader" in recent years had made her a "poor daughter, sister, partner and friend", and that The Arrival of her son Finn last October "means I now make a different Choice ".Ms Davidson clashed with Boris Johnson over Brexit during a live BBC TV debate ahead of the EU referendum
When she returned to the Scottish Parliament from maternity leave in May, she told Bbc Scotland that it would be "tough to tear myself away from the wee man" But that "having a child and Coming Back to work is a part that lots of women play".
Under her leadership, the Scottish Conservatives More Than doubled their number of seats at Holyrood in the 2016 Election - making The Party the second biggest behind the SNP. The Following year it increased its MPs from one to 13 in The General Election .
That relative success had seen her tipped as a future UK Tory leader and Prime Minister , But she insisted she had no interest in The Job - and that she was focused only on replacing Nicola Sturgeon as first Minister of Scotland at the next Holyrood Election in 2021.
She also said in her resignation statement that her party's electoral successes had paled in significance compared to The Role it had played in The Campaign to keep Scotland in the UK during the independence referendum campaign.
Analysis by Sarah Smith , Scotland editorMs Davidson sought to position herself as The Defender of The Union between Scotland and England
Ruth Davidson 's unique selling point has always been that she doesn't look like and doesn't sound like a Tory, so she could persuade people who had never previously considered voting Conservative to at least give them a hearing.
She was helped enormously by the fact that the dominant issue in Scottish politics throughout her eight years as leader has been Scottish independence.
Since Boris Johnson became PM we have seen an opinion poll that suggests 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.
Her spokesman today would not be drawn on whether she might be persuaded to play a leading role in a future referendum campaign.
Responding to her resignation, Mr Jack paid tribute to her "inspirational and transformational" leadership, adding that she had "made the Scottish Conservatives the only credible challenger to the SNP in Scotland".
Scottish Labour leader Richard Leonard said the loss of Ms Davidson would be a "real blow to her party" and would demonstrate that Mr Johnson was already losing support and credibility within his own ranks.
Scottish Greens co-leader Patrick Harvie said Ms Davidson was due some credit for "ending the pretence and resigning", while Scottish Lib Dem leader Willie Rennie said Ms Davidson had "run out of reasons to stand by this dangerous and power hungry Prime Minister ".