Willie Rennie has been praised for saving the Scottish Liberal Democrats "from oblivion" after announcing he will stand down as party leader following a decade in the role.
Mr Rennie said he had decided to quit after fighting "11 elections and referendums over 10 years and a global pandemic".
He said it was "time for a fresh face to lead our party forward" but he would continue as MSP for North East Fife after holding his seat in the recent Holyrood election.
Alex Cole-Hamilton is the front-runner to replace him and the Edinburgh Western MSP last night paid tribute to his "charm and relentless positivity".
He said: "It has carried both me and the Liberal Democrats through some of our darkest moments and it is not overstating things to say that he has saved our party from oblivion and obscurity on more than one occasion."
Mr Rennie took over the leadership following the party’s disastrous 2011 election, when the party’s vote collapsed and it lost 11 of its 16 seats following a voter backlash against Nick Clegg’s decision to enter the coalition with the Tories at Westminster.
Nick Clegg with Willie Rennie (left) during a press call at North Queensferry, Scotland October 24, 2007
The Lib Dems have not recovered since at either Westminster or Holyrood, and they lost another seat in May’s Scottish Parliament election, dropping to four. However, Mr Rennie massively increased his majority in his seat to 7,448.
Sir Ed Davey, the UK Lib Dem leader, led tributes to him, saying: "From banging the drum on mental health and education to those amazing photo-ops, Willie Rennie has been a fantastic leader, he is the best of us."
Nicola Sturgeon said "political leadership takes its toll" and she had "always respected his commitment and decency" despite their political differences.
Announcing his decision to quit, the 53-year-old said: "Over the last decade there have been both gains and losses along the way, but I have enjoyed every effort. I love a good campaign.
“But it is time for a fresh face to lead our party forward. The new Leader will have my full support in writing the next bright chapter of the Scottish Liberal Democrats’ story."
He said the party under his leadership had "moved the debate and delivered change" on better mental health services, education and a more liberal justice system.
Mr Rennie added: "Scotland deserves a strong progressive alternative to the twin nationalisms represented by the SNP and Conservatives".
Willie Rennie with a ram during a visit to Mill House farm in Kelty, Fife in 2017
Willie Rennie leader of the Scottish Liberal Democrats, water skies during a European Election campaign event at Water Ski & Wakeboard Scotland on May 21, 2019 in Dunfermline, Scotland
Credit: Getty Images
Scottish Liberal Democrat leader Willie Rennie listens to exchanges during First Minister's Questions in the Scottish Parliament on the eve of the UK general election, on June 7, 2017
Credit: Corbis News
Mr Cole-Hamilton, who won his seat in May with a huge majority of almost 10,000, said: "His legacy as leader will be vast and long lasting, principally focussed on those at the margins of society while ensuring that Scotland has had and will continue to have strong, liberal voices at every level of public life in our country."
Anas Sarwar, the Scottish Labour leader, said: "Anas Sarwar also said: "It’s not been a quiet 10 years in Scottish politics.
"Throughout it all, Willie Rennie has led with humour, positivity, energy and compassion. He is a good friend and an inspiration to all those that love a photo-op."
Jackson Carlaw, the former Scottish Tory leader, tweeted that Mr Rennie was "a delightful & decent man who has led with integrity, guile & good humour through thankless times for his party."