Scotland's former deputy first minister, John Swinney, announced on Thursday he would stand to succeed Humza Yousaf as leader of the country's governing Scottish National Party (SNP).
The announcement follows Yousaf's announcement on Monday that he would resign as party leader and Scotland's first minister once a successor has been chosen to head the devolved government.
Swinney, 60, who led the pro-independence SNP from 2000 to 2004, said he was running "to unite the SNP and unite Scotland for independence", despite polls showing stalled support for splitting from the UK.
"I intend to stand for election as leader of the Scottish National Party," Swinney told an audience of SNP supporters in Edinburgh.
"I want to build on the work of the SNP government to create a modern, diverse, dynamic Scotland that will ensure opportunity for all of our citizens."
Outgoing leader Yousaf, 39, has been in charge for little more than a year.
He was forced out after ditching his junior coalition partners, the Scottish Green Party, in a row over climate policy.
He had struggled to convince in the role he inherited from predecessor Nicola Sturgeon, with the SNP embroiled in an SNP funding scandal and a challenging domestic policy landscape.
Potential successors for the SNP leadership have until Monday to declare their candidacies.
All eyes now turning to former finance secretary Kate Forbes to see if she makes a bid for the top job.
Forbes, 34, finished a close second to Yousaf in a bitterly fought leadership contest last year but her socially conservative views are again seen as a potential hindrance.
With the SNP heading a minority government in the 129-seat Scottish parliament, as leader she would need the support of another party to either form a governing coalition or pass pieces of legislation.
The only likely allies are the Greens but they have socially liberal positions on a host of issues and have indicated they would not be eager to work with her.
In his remarks, Swinney was keen to praise Forbes, in a sign the pair may have agreed a pact to avoid another acrimonious leadership fight.
Insisting he wanted Forbes "to play a significant part" in his governing team, he lauded her as "an intelligent, creative, thoughtful person who has much to contribute to our national life".
The new SNP leader, expected to be in place by early June at the latest, will need sufficient votes in the Scottish parliament to be elected first minister.
The government, which survived a no-confidence vote on Wednesday brought by opposition parties, is currently two votes short of an overall majority.
The ructions in the SNP, which has dominated Scottish politics for nearly two decades, are being closely watched in London, ahead of a UK general election later this year.
The SNP currently holds 43 seats in the UK parliament.
The UK's main Labour opposition is hoping for a resurgence in its former stronghold north of the English border to help it win an outright majority in the general election.
