MSPs will vote for Scotland’s newest first minister following the Holyrood elections.
John Swinney, the serving First Minister, said he is confident he will win the vote.
However, all five other parties at Holyrood have said they will also put their leaders up for the top job.
The SNP won 58 seats at the Scottish Parliament elections, making it by far the largest party but short of the 65 seats needed for a majority.
Mr Swinney will need the help of at least one other party, which in previous years has come from the Greens.
Ahead of Tuesday’s vote, the party has called on Mr Swinney to honour his promise to introduce a vote on a second referendum on the first sitting of his new government.
Mr Swinney promised during the campaign that a new SNP administration would bring forward a vote to approve the development of a Section 30 order, which would be needed to transfer powers to hold a referendum from Westminster to Holyrood.
Since the powers are reserved, the vote would act as a message to express the will of the Scottish Parliament and pressure the UK Government to approve a second vote on the union.
Gillian Mackay, co-leader of the Scottish Greens who will stand for the first minister vote, said Scotland had voted for a pro-independence majority Parliament, “and that must be respected”.
She added: “If John Swinney is elected first minister on Tuesday, then his new government must bring forward the promised parliamentary debate and vote on Scotland’s right to choose at the first available opportunity.”
Mr Swinney told voters during the election campaign that a pro-independence majority of SNP MSPs would be a mandate. Having failed at that, the first minister has insisted the pro-independence majority the party has along with the Greens still counts as a mandate.
Ms Mackay said: “It is welcome that, now the election is over, the SNP appears to recognise that Green votes are also independence votes. But recognition is not enough.
“The First Minister must follow through on his promise and offer the clear roadmap to independence that Scotland deserves and voted for.”
The Scottish Conservatives urged Mr Swinney to show some “common sense” and rule out another deal with the “anti-oil and gas” Greens.
Russell Findlay, the party’s leader, claimed the SNP’s “anti-oil and gas agenda” would harden if he “ends up at the mercy of the Greens”.
Mr Findlay, speaking ahead of the Aberdeen South by-election, said that while the SNP leader “likes to pretend” he supports Scotland’s oil and gas sector, his party maintains a presumption against new drilling in the North Sea.
He said: “There are significant concerns that the SNP’s anti-oil-and-gas agenda will harden if Swinney ends up at the mercy of the Greens, who he previously brought into government and who would turn off the taps overnight.
“It would be basic common sense for (Mr) Swinney to explicitly rule out any form of new coalition or pact between the SNP and Greens ahead of parliament voting to confirm who becomes first minister.”
Speaking to the Press Association on Tuesday, the First Minister said he was confident he could lead the SNP into a fifth consecutive term in government.
He said: “The people of Scotland were crystal clear in the election – they want the SNP to lead the Government.
“We were elected with 58 members of the Scottish Parliament, we’ve got a commanding lead over the other parties, and I look forward to putting forward my candidacy to be first minister tomorrow and to take forward a government that will serve the people of Scotland.”
He added: “I’m confident that I can win the vote tomorrow and to make sure that I continue to lead a government that will deliver for the people of Scotland.”
The election of the first minister will take place on Tuesday afternoon, with the winning candidate likely to be sworn in at the Court of Session on Wednesday and appoint a cabinet that afternoon.
Thursday will be taken up by the vote to confirm the appointment of ministers, with the inaugural First Minister’s Questions of the parliamentary term due to take place next week.
