SNP deputy leader contender Keith Brown has won support from two Scottish ministers.
Minister for Learning and Scottish Languages Alasdair Allan and Environment Minister Paul Wheelhouse said the former Royal Marine was the best person for the job.
Their support means the transport minister now has the backing of more than half the SNP’s Holyrood group.
Both Mr Allan and Mr Wheelhouse also see Mr Brown as deputy first minister, standing in for First Minister in waiting Nicola Sturgeon.
Training, Youth and Employment Secretary Angela Constance has ruled herself out of the job while Dundee East MP Stewart Hosie would be ineligible not having a seat in the Scottish Parliament.
Mr Allan, MSP for the Western Isles, said it was impressive the SNP could produce three such talented candidates.
“Thinking about the job that will face the depute leader, though, it seemed clear to me that we needed someone with a certainty of touch, incredible organisational skills, huge stamina and a sense of humour to see them through,” he said.
“We need someone with a good working relationship with Nicola Sturgeon and Keith’s shown he has that in the years he’s been a minister in her government team. She will need someone who can take on some of the workload while she runs her government and the party.”
Mr Wheelhouse said: “He is unflappable, retains his sense of humour and is hugely respected.
“Keith has excellent organisational and leadership skills that he demonstrates as a minister and is an excellent performer in the chamber and in media interviews which will be essential in deputising for Nicola.”