Eluned Morgan is expected to be named the new leader of Welsh Labour and likely first minister of Wales on Wednesday.
She will replace Vaughan Gething, who announced his resignation last week after a torrid four months in office, featuring rows over donations and sacked ministers.
Baroness Morgan, 57, the current Welsh health minister, is the only contender to be the Welsh Labour Party’s new leader, with nominations closing at midday.
The Welsh parliament is currently on recess until September, and it would need to be recalled for her to take over sooner.
When confirmed, she would become the first woman to lead the Welsh Government.
Welsh Conservatives have already said they will be asking for a recall if she wins, with party leader Andrew RT Davies saying this would “give Wales greater stability”.
But Plaid Cymru has repeatedly called for a snap election with party leader Rhun ap Iorwerth insisting that Baroness Morgan’s leadership will be “more of the same”.
He said: “Eluned Morgan will today become the third Labour leader in Wales in three months.
“But they won’t allow an election, and will do all they can, including teaming up with the Conservatives, to stop that happening, it seems.”
Mr RT Davies has previously branded calls for a snap Senedd election “hot-headed”.
If an election were held, Senedd rules mean another one would have to be held in 2026.
Labour’s ruling body had originally set a timeline of having a new Labour leader in place on September 14, with them taking over as first minister on September 18.
Baroness Morgan has won the support of the majority of the Labour group, with few MSs, including Hannah Blythyn and outgoing First Minister Vaughan Gething not having indicated support for anyone.
Baroness Morgan has been the Senedd member for Mid and West Wales since 2016 and a peer in the House of Lords since 2011.
She is currently listed as being on a leave of absence in the Lords.
From 1994 to 2009 Baroness Morgan was a member of the European Parliament.
Baroness Morgan has promoted herself as a “unity candidate”, with the Labour group having become fractured in recent months following a series of rows involving Mr Gething and donations he took during the last leadership election earlier this year.
The race to replace the First Minister began after four members of his government quit en masse last week, criticising his leadership.
During the last leadership race Mr Gething took a £200,000 donation for his leadership campaign from a company owned by a man twice convicted of environmental offences, which led to some members of his own party criticising his judgement.
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 Ms Blythyn as a minister.
All the other potential candidates who were expected to run in the Labour leadership race have announced their support for Baroness Morgan.
This includes Jeremy Miles, who ran against Mr Gething in the last leadership race and was one of the four people to quit his government last week.
Mr Miles made a surprise move by becoming the first person to publicly endorse Baroness Morgan on Sunday before she had officially announced her candidacy.
