When Nicola Sturgeon stood down as First Minister and SNP leader last year, MPs, MSPs and political observers alike were struck by the significance that the party would be embarking on its first leadership election in almost 20 years.

Now the party is facing its second leadership contest in just over 13 months - or perhaps a change of leader without a race - following reports that Humza Yousaf is to resign today. He is to hold a press conference at Bute House at noon when he is expected to announce that he is standing down.

So who are people discussing as contenders to be the next SNP leader and First Minister?

Former finance secretary Kate Forbes - who was narrowly defeated by Mr Yousaf in last year's contest - is the bookies favourite.

Leading bookmakers Coral puts Ms Forbes - who pitched herself in the last SNP leadership contest as the change candidate - is the odds-on favourite at 1-2 to be the next First Minister.

The Skye, Lochaber and Badenoch MSP is perhaps the most likely replacement after she narrowly lost to Mr Yousaf in the fiery leadership contest to replace Nicola Sturgeon just over a year ago.

And as finance secretary under Ms Sturgeon, Ms Forbes has been known to help her government through tough crises, stepping into the role and delivering a budget at short notice after her predecessor, Derek Mackay, resigned in disgrace in 2020.

A Free Church of Scotland member, Ms Forbes’ first run at the leadership was not smooth sailing as her stance on social issues is at odds with many within her own party, particularly her opposition to gender reform.

A key obstacle in her leadership, however, would be the Scottish Greens, they have previously ruled out working with her over her views so it is unlikely she would command the support to effectively rule.

In the last leadership contest, Ms Forbes did not have the backing of most of her own SNP MSPs but did win over a significant number of members, losing the closely-fought leadership election by 47.9% of the vote compared to Mr Yousaf’s 52.1%.

READ MORE: No confidence vote: Why better for Humza Yousaf to quit now

John Swinney

The loyal deputy first minister to Ms Sturgeon could throw his hat in the ring as an SNP MSP with significant experience.

He has been an MSP since the Scottish Parliament’s inception in 1999, serving North Tayside, and previously representing the same constituency at Westminster in 1997.

Mr Swinney previously led his party in Holyrood between 2000 and 2004 during the SNP’s time on the opposition benches.

He has held a raft of cabinet positions, including education and finance and resigned at the same time as Ms Sturgeon.

He also ruled himself out of the 2023 leadership race, stating he had to put his young family first. However, the SNP politician could take the reigns to unite his party in a time of turmoil.

Health Secretary Neil Gray - and ally of Mr Yousaf and also seen by many in the party as a safe pair of hands - is second best in the betting at 2-1, while Cabinet Secretary for Net Zero Mairi McAllan is 7-2.

"Kate Forbes fell just short in the last SNP leadership race, but our betting suggests she is the favourite to replace Humza Yousaf as the next First Minister," said Coral.

"Health Secretary Neil Gray has also been popular in our market."

The Herald: Humza Yousaf and Kate Forbes pictured at a hustings at the SNP's leadership contest last year. PA.

The wealth of experience held by Mr Gray could make him a likely contender for leadership.

He is thought to be the closest ally of Mr Yousaf but may be able to unite Parliament.

He is a former MP and became an MSP in 2021 serving as a culture and international development minister before being promoted to Economy, Fair Work and Energy Secretary around a year later.

He stepped up to become Health Secretary following the resignation of Michael Matheson.

READ MORE: SNP's Kate Forbes hopes Scottish Greens will 'embrace' her

Ms McAllan's  dropping of a climate target announcement earlier this month triggered the events leading to the collapse of the Bute House Agreement and Mr Yousaf's expected resignation.

Due to go on maternity leave in the summer, Ms McAllan's family time maybe short lived were she to become First Minister with an general election probably just months ahead. Some in the party believe she may not decide to stand in the circumstances.

The Clydesdale MSP has been tipped as a future leader as she quickly moved up the ranks despite only being elected in 2021.

At the age of 31, Ms McAllan would become the youngest first minister, but her portfolio in Holyrood shows she is already capable of handling a significant brief.

The party’s rising star was given a ministerial post for environment, biodiversity and land reform in May 2021, shortly after being elected.

But, under Humza Yousaf, she quickly ascended to a cabinet post just two years later, taking on the Transport, Net Zero and Just Transition portfolio.

Her brief was widened further in February 2024 after Neil Gray was moved to Health Secretary. She became Wellbeing Economy, Net Zero and Energy Secretary.

Ms McAllan announced she was expecting her first child in February 2024, adding she planned to take maternity leave in the summer with a scheduled return for March 2025.

Education Secretary Jenny Gilruth could also throw her hat into the ring.

The former teacher represents Mid Fife and Glenrothes and her brief is one of the toughest as she faces pressure to address the increasing issue of violence in schools.

The Herald: Humza Yousaf pictured with last year SNP leadership candidates Ash Regan, left, and Kate Forbes, right, as the results of the contest was announced. Photo PA.

She has also held transport minister briefs and Europe, migration and international development minister.

However, it is thought that rather than a large list of candidates, the party may favour a head to head between Mr Gray and Ms Forbes should there be a leadership election or possibly someone such as Mr Swinney taking over in an interim role until after the general election when a leadership contest would be held.