Voting in the contest to succeed Nicola Sturgeon and become Scotland’s next first minister will begin later on Monday.
Ballot papers are being sent out to tens of thousands of SNP members, who are tasked with choosing their party’s new leader.
With the SNP the largest party in the Scottish Parliament, whoever wins the contest will go on to become the country’s sixth first minister.
Just hours after voting gets under way, the candidates will take part in a live TV debate on Sky News – the third televised clash of the leadership campaign so far.
The leadership contest is taking place after Ms Sturgeon last month announced she was quitting the job she has had for more than eight years – making her the longest-serving Scottish first minister to date.
Three candidates are in the running for the top job in Scottish politics – with Finance Secretary Kate Forbes, Health Secretary Humza Yousaf and former community safety minister Ash Regan all standing.
With Mr Yousaf having received the backing of John Swinney, the outgoing Scottish Deputy First Minister, the Scottish Health Secretary is regarded by some as being the party’s preferred candidate.
And while some polls have put Ms Forbes ahead amongst the Scottish public, it is SNP members alone who will make the choice.
But the single transferable voting system being used means second preferences could be key in determining the next SNP leader.
Party members will be asked to rank the three candidates in order of preference, and if no single candidate secures more than 50% of votes on first preferences, the person in third place will be eliminated.
Their second preference votes will then be distributed amongst the two remaining candidates in order to find the winner.
The company Mi Voice – which runs all internal SNP elections – will be sending out emails to party members when voting opens at noon.
Paper ballots have also been sent out to those members who have requested them, with those also due to arrive on Monday.
Members have two weeks to cast their vote, with the ballot closing at noon on March 27.
An SNP spokesperson said: “SNP members will receive their ballots via email today and have until the morning of March 27 to cast their votes – the day the next leader will be announced.
“The ballot is being operated by an independent third party who will ensure the process is free, fair, and well-run.”
