The Scottish Tory leader had supported home secretary Sajid Javid, who was eliminated in the fourth round yesterday afternoon.
She swiftly endorsed Michael Gove, saying the environment secretary was “smart, articulate and a real details man”. He was beaten into third place by foreign secretary Jeremy Hunt.
It comes after nearly a year of speculation about a plot among senior Scottish Tories to try and block Mr Johnson from reaching 10 Downing Street, dubbed ‘Operation Arse’. Senior figures fear that the former foreign secretary is toxic in Scotland and could damage the party’s electoral chances.
Mr Javid and Mr Gove were the only two ministers from outside Scotland given speaking slots at this year’s Scottish Conservative conference.
On social media, Ms Davidson said she was “proud of the way Saj has acquitted himself throughout this contest”. “I think he’s won a lot of admirers,” she said.
The SNP mocked the Scottish Tory leader for what they claimed was “the curse of Ruth Davidson”.
“She’s now got some run of form in backing the loser,” SNP MSP George Adam said.
“Ruth Davidson hitched her wagon to Sajid Javid’s doomed campaign and, embarrassingly, couldn’t get a single one of her MPs to support him ... Ruth Davidson used to be seen as a major figure in the Tory party. Now she’s become a complete irrelevance.
“A hardliner whose lies she once called out is about to become her new boss and the next Prime Minister. That will be an unmitigated disaster for all of us.”
Ms Davidson’s streak of bad luck was surpassed by the East Renfrewshire MP Paul Masterton, who backed Matt Hancock, then Rory Stewart and finally Mr Javid.
After the home secretary was eliminated, he tweeted: “WHY AM I SO BAD AT THIS?! #sorrySaj.”
At the final count, there were six Scottish Tories publicly backing Mr Gove, including the Scottish secretary David Mundell and four supporting Mr Johnson.
Gove supporter Stephen Kerr said he was “proud to have supported his campaign and everything he stands for”.
The only Scottish Conservative MP celebrating Mr Hunt’s narrow victory over Mr Gove was John Lamont. He said Mr Johnson’s status as favourite would have no bearing on the contest to come, and warned the former foreign secretary would face tough questions, particularly over his profile and popularity in Scotland.
“The scrutiny on both candidates from the media and from members will be much more intense,” Mr Lamont said. “That will especially be the case in relation to their approach to Scotland and protecting the Union.”