Scottish Labour's stand-in leader Alex Rowley has ruled himself out of the race to replace Kezia Dugdale.
The Mid Scotland and Fife MSP said the next Labour leader must be ready to replace Nicola Sturgeon as First Minister and said he has "no ambition" to do this.
"Whoever becomes the next leader of the Scottish Labour party should be focussed on ensuring that they become the next First Minister of Scotland - I'm absolutely clear on that and I think we can do that.
"I've no ambition to be the First Minister of Scotland - it's never something that I saw myself doing.
"I have no intention of running for leader because whoever is in that job, their focus should be on becoming the next First Minister."
Mr Rowley, a key ally of former Prime Minister Gordon Brown, said he was more content to help build the "labour movement from the grassroots up."
He added: "I'm much more comfortable doing that than I would be trying to be the First Minister - but I think you've got to be clear: Do you want to be the next First Minister? I don't and it would be wrong therefore for me to run as the leader of the Labour party in Scotland, as the next leader of the Labour party in my view should be able to become the next First Minister of Scotland."
Mr Rowley is now interim leader and will remain in this role until a replacement for Ms Dugdale is selected. He is the second big hitter to rule himself out of standing after Jeremy Corbyn closest ally in Scotland also ruled out a leadership bid.
The contest is now shaping up as a two-way contest between former union official Richard Leonard and the ex-Deputy leader Anas Sarwar. The party's executive committee in Scotland will meet on Saturday week to discuss the contest.
Mr Rowley played down suggestions that Ms Dugdale's departure was a sign of the Corbynite faction tightening its grip on the party north of the border.
"It's not something I recognise," he said.
He added: "We're stronger than we've been in a long time. We're more united, we're united around a manifesto for the many not the few. That is where our policy platform sits, that was our policy platform launched at a UK level by Jeremy Corbyn, launched at a Scottish level by Kezia Dugdale.
"You saw in the last few weeks when Jeremy Corbyn was in Scotland that there is widespread support right across the party for that policy platform. "
Scotland's biggest trade union has thrown its weight behind Mr Rowley remaining as interim leader for an extended period while a decision is taken on the next leader.
Unite's Scottish Secretary Pat Rafferty said: "We urge the party to reflect upon this turn in fortunes and consolidate, not to act in undue haste on any succession plan," he said.
"There is no need to rush to a leadership election. Under Alex Rowley's interim leadership we are confident that the voices of Scotland's working people will be heard loud and clear at Holyrood.
"This is not about the next four weeks. It is about the next four years. This is an opportunity to reflect upon what the Scottish Labour Party stands for. Let's seize it and build for the future."