Voting to elect a new Scottish leader opened on Monday (13), with all three candidates pledging to reinvigorate outgoing first minister Nicola Sturgeon's push for independence.
Sturgeon's independence drive hit trouble after the UK government blocked her plans to hold a fresh referendum on the issue.
The vote is the Scottish National Party's first full leadership battle since 2004.
Sturgeon, who quit last month as both SNP leader and Scottish first minister, had also became embroiled in controversy over her handling of a transgender rights row.
The leadership contenders include two women - one a devout Christian opposed to same-sex marriage - and a Muslim man.
Rising star and current finance secretary Kate Forbes, 32, sparked controversy after she said she would have voted against same-sex marriage had she been a member of the Scottish parliament when the reform passed in 2014.
Forbes is a member of the Free Church of Scotland, Scotland's second largest denomination, which opposes same-sex marriage and abortion.
Health secretary Humza Yousaf, 37, has won the backing of Sturgeon allies. He is the first non-white and Muslim cabinet member of the Scottish government.
The third candidate - Ash Regan, a 38-year-old former minister - has pledged to restore unity to the party.
In a debate on Thursday (9), Yousaf questioned whether Forbes' personal convictions put other people's rights at risk.
People want a first minister who does "not believe that they are morally inferior" and who would "protect" and "advance" their rights, he said.
Forbes has defended her views as a matter of personal conscience but they have left her out of tune with the SNP's centre-left base.
Despite this, an Ipsos poll of all voters last week put her ahead on 32 per cent, with Yousaf on 24 per cent and Regan on eight per cent.
But Yousaf is widely seen as the preferred candidate for SNP voters.
In last week's debate, Forbes questioned whether he had the mettle to take on the UK government over its refusal to grant permission for another independence referendum.
Regan meanwhile, claimed she alone had a credible plan to build support for independence and panned her rivals' approach as "wishy washy".
(AFP)
Voting starts for new Scotland leader as Sturgeon’s allies back Yousaf
The vote is the Scottish National Party’s first full leadership battle since 2004
Bob Blackman MP speaks during the event
Pope Francis greets Narendra Modi on the sidelines of the G7 summit near Bari, Italy, in June last year, as Italian prime minister Giorgia Meloni and then British prime minister Rishi Sunak look on