Anas Sarwar - the party's current Constitution spokesman at Holyrood lost out to Leonard in the race to replace Kezia Dugdale three years ago and will be the frontrunner to lead the party after Leonard’s departure. One of the party's best performers in the Scottish Parliament.
Jackie Baillie - the current Deputy leader in Scotland one of the Labour’s most effective and experienced MSPs. She may be viewed as a safe pair of hands to lead the party through the next few months as interim leader and avoid a potentially messy leadership campaign in the build up to a Holyrood election. The party could then look to a new candidate for the future after the May vote.
Monica Lennon - the party's health spokeswoman at Holyrood could emerge as a preferred candidate of the left. She broke with the party line in the aftermath of the general election defeat and suggested that she could be supportive of an independence referendum amid growing concerns that much of the party's traditional support base was now in nationalist camp.
James Kelly - The Glasgow MSP lead an attempted coup against Leonard last September when he published a letter calling for him to quit. Kelly was soon followed in his public demands by fellow MSPs Jenny Marra, Mark Griffin and Daniel Johnson. But he would be an outside prospect for the party leadership.
Ian Murray - Another outside prospect, but Murray is one of Labour's most effective Scottish politicians and party's only MP north of the border. He could perhaps see this is an opportunity to seek a move to Holyrood from Westminster, following the route of Scots Tory leader Douglas Ross, and lead the party north of the border. Securing a Holyrood seat may be a problem at this late stage before an election. He may also be reluctant to give up his Westminster Edinburgh South seat having only been returned just over a year ago.