Carwyn Jones has long been considered a likely leadership candidate
A likely contender to take over from Welsh Labour leader Rhodri Morgan has warned his party it can no longer rely on its core vote to win elections.
In a speech, Bridgend AM and assembly government minister Carwyn Jones said it was time to "make accommodations" with occasional Labour voters.
He was speaking at an event at the National Eisteddfod at Bala, Gwynedd.
First Minister Mr Morgan has said he expects to step down around the time of his 70th birthday next month.
Mr Jones, the assembly government counsel general, told a fringe meeting organised by Labour's Welsh language discussion forum Cymdeithas Cledwyn that the party needs to be honest about its current level of public support.
It follows Labour's poor performances in European, local and assembly polls in recent years.
In the European poll in June, Labour was humiliated when it failed to come first in a Welsh election for the first time since 1918 and the Conservatives topped the poll.
Mr Jones urged the party to reach out, to both people who occasionally vote for it and those who have not voted for the party for a long time, or face the prospect of no longer winning elections in Wales.
He also admitted Labour faces challenges winning back support from ethnic minority voters because of the wars in Iraq and Afghanistan.
He called for the party to put itself at the heart of a "fair play coalition", or "chwarae teg coalition" founded on principles of fairness, justice and opportunity.
No Labour AM has formally declared they intend to stand for the party's leadership.
But Mr Jones, Merthyr Tydfil and Rhymney AM Huw Lewis and Gower AM and Health Minister Edwina Hart are all thought to be preparing campaigns.