The SNP is set to hold its first leadership election in almost two decades after Nicola Sturgeon announced her intention to resign on Wednesday morning. 

Ms Sturgeon said that she had already asked the SNP to begin the process of electing a new party leader, and that she would “remain in office until my successor is elected”. 

A new leader is expected to be announced within the next six to eight weeks following a vote by party members, in a race in which the SNP's push for independecne will take centre stage. 

Kate Forbes, the party's finance secretary before she departed on maternity leave, is seen as an early frontrunner, alongside Angus Robertson, the party's former Westminster leader, and John Swinney, the Deputy First Minister. 

Here, we outline how a new SNP leader will be elected.

How will the SNP elect a new leader? 

The SNP's constitution states that all leadership candidates must obtain at least 100 nominations from party members from at least 20 of the party's local branches in order to stand. 

If more than one candidate achieves this threshold, an election takes place in which all party members are eligible to vote. The election is run on a one-person-one-vote postal voting system. 

There was no leadership election in 2014 when Ms Sturgeon became First Minister as she ran unopposed following the resignation on Alex Salmond. 

The last time SNP members voted for a leader was in 2004 when Mr Salmond beat John Swinney with more than three-quarters of the vote. Ms Sturgeon withdrew from that race and become the party's deputy leader. 

Who nominates the new First Minister? 

The new First Minister is nominated for appointment by Members of the Scottish Parliament (MSPs) - unlike the Prime Minister in London who is appointed by the King under the Royal Prerogative.

Under section 46 of the Scotland Act, the Scottish Parliament has 28 days to nominate a successor once a First Minister has tendered their resignation to the King. 

This could theoretically be any MSP, but in practice it is always the leader of the party with the most MSPs at Holyrood. 

The Presiding Officer of the Scottish Parliament invites each candidate to speak in favour of their candidacy. 

MSPs are then asked to cast their vote - a separate vote is held for each candidate - and the Presiding Officer will then announce the winner. The successful candidate is elected by a simple majority.

The Presiding Officer then recommends to the King that he appoint the winning candidate.

How are they sworn in? 

The new First Minister is sworn in a day or two after their official nomination at the Court of Session in Edinburgh, Scotland's supreme civil court. 

They are appointed with a Royal Warrant, which is a legal document authorised by the King. 

The Lord President of the Court of Session firstly administers the oath of office, or the “official declaration”. They then declare the new leader as Keeper of the Scottish Seal, before administering the declaration of allegiance to the King. 

The new First Minister bows their head in agreement to these declarations with their right hand upheld. 

The First Minister also becomes a member of the Privy Council of the United Kingdom by custom, which advises the King on exercising his prerogative powers. 

When will we know?

The short answer is: we do not know. The details of the leadership race will be decided by the SNP's national executive committee and have not yet been announced.

Who is likely to take over?

The bookmaker William Hill ranks Angus Robertson, Scotland's Constitution Secretary, as first-placed in the race to succeed Ms Sturgeon. 

Mr Robertson formerly led the party at Westminster and is among the most powerful figures in the SNP.

Kate Forbes, the Finance Secretary, is another potential successor and is due back from maternity leave in the coming weeks.

Ms Forbes has been a rising star within the party since being thrust into the limelight to deliver the Budget in 2020 after her predecessor Derek Mackay resigned in disgrace.

But Ms Forbes is believed to be at odds with the party over a number of social issues, including the push for gender reforms - a vote she missed while on maternity leave.

Humza Yousaf, the Health Secretary, may also take a run at the leadership.

However, the controversial passage of the Hate Crime and Public Order (Scotland) Act when he was justice secretary and the ongoing crisis in the NHS could dent his chances.

What next for Nicola Sturgeon?

The First Minister will continue as an MSP from the backbenches, at least until the 2026 Holyrood election.

She said that she planned to continue to campaign on criminal justice reforms, improving the experience of young people in care, and Scottish independence.

Ms Sturgeon also told Vogue magazine in 2021 that she would consider becoming a foster parent when her time in office is over.