Former MSP Mike Russell has become the third contender for the position of Scottish National Party leader.
Mr Russell is former party chief executive
Mr Russell, who also served as the SNP's chief executive, said it would require "courage" to undertake radical change in the party.
He has joined MSPs Roseanna Cunningham and Nicola Sturgeon in the race for the top job.
Mr Russell lost his Scottish Parliament seat at the last election after being placed too low in the party rankings.
However, the fact that he is no longer an MSP does not prevent him from standing in the contest to replace John Swinney.
At a news conference in Edinburgh, Mr Russell said he had been dismayed to hear political opponents crowing about disunity and despair in the SNP.
Declaring his intention to stand, 50-year-old Mr Russell said: "This SNP leadership election requires to be a direct, open and honest debate by all of the party to redefine its goals and find a new way forward.
"We in the SNP have to undertake radical change, to create a new way of politics engaging with people, their lives and aspirations. That requires courage.
"It is dismaying to hear our opponents crowing about dither, defensiveness, disillusionment, disunity, defeatism and despair in the ranks of the SNP."
Mr Russell told reporters: "What we need now is determination, dignity, directness and honest, open debate.
"I want to lead a party that is a broad church, full of ideas, with a membership that contributes positively at every level."
The former chief executive had been the SNP election campaign director from 1994 until his election in 1999.
He was a list MSP until the elections in May 2003 when he lost his South of Scotland seat.