Welsh Health Secretary Eluned Morgan has officially announced she is running to replace outgoing First Minister Vaughan Gething, who lasted just four months in the post.
Baroness Morgan will be standing on a joint “unity” ticket with rural affairs minister Huw Irranca-Davies, who would become deputy first minister.
They have received a groundswell of support from across the Labour benches, including from Mr Gething’s rival in the last leadership race, Jeremy Miles.
Their announcement on Monday comes after Mr Gething was forced to announce his resignation as First Minister and Welsh Labour leader last week, after four members of his cabinet quit en masse in criticism of his leadership.
However, she would not become first minister until she is confirmed in a vote in the Senedd.
If no one else stands, the Welsh Tories have said they will ask for the Welsh Parliament to be recalled from its summer recess to enable Baroness Morgan to take over.
Conservative leader Andrew RT Davies has said this will “give Wales greater stability” arguing the country would be “without a functioning government for months over the summer” if the vote is delayed. The assembly is due to return on September 16.
In a statement, Baroness Morgan said: “I am proud to stand as a candidate to be the next leader of Welsh Labour, driven by a passion to serve the people and reset the relationship between the Government and the people of Wales.
“I am delighted to be teaming up with my fantastic colleague, Huw Irranca-Davies, who shares my passion and experience in government and strong sense of public duty. Together, we are committed to putting Wales back on track.
“In the coming days, we will set out our priorities to improve public services, create better, greener jobs and empower our communities.
“Our focus will be meaningful change and building a brighter future for communities across Wales.”
If Baroness Morgan succeeds, she will be the first female leader of Wales.
“Eluned has the energy and experience to lead and deliver for the people of Wales and harness the opportunity of working with a new UK Labour Government.
“Working together and with our leadership team, our Welsh Labour movement will keep working to improve people’s daily lives and standing up for a fairer and greener Wales.”
Deputy first minister positions are uncommon in Wales, with the roles having only been given to opposition groups working in coalition with the Labour leadership in the past.
Welsh Labour’s ruling body set out a timetable for replacing Mr Gething on Saturday, members having until Wednesday to announce their candidacies.
Candidates must have six nominations to enter.
A new Labour leader will be in place by September 14 and, subject to a vote in the Senedd, will take over as first minister on September 18.
Mr Gething announced last Tuesday that he was standing down just four months after taking on the role.
He has faced a series of rows over a £200,000 donation to his leadership campaign from a company owned by a man twice convicted of environmental offences.
Last month Mr Gething lost a vote of no confidence in the Senedd, after rows over the donation, and his decision to sack Delyn MS Hannah Blythyn as a minister.