South African deputy president Cyril Ramaphosa on Thursday won the support of Cosatu, the biggest union federation, to be the ANC partys next leader, boosting his chances of taking national power.
The African National Congress (ANC), which is currently headed by scandal-tainted President Jacob Zuma, is due to choose its new leader in December next year.
The party leader becomes its automatic presidential candidate in the next general elections, with the ANC still the strong favourite to win the 2019 vote despite a fall in nationwide popularity.
Cosatu general secretary Bheki Ntshalintshali said it had "resolved to support and lobby" for Ramaphosa, a former anti-apartheid activist and trade unionist who helped negotiate the end of white-minority rule in 1994.
The 64-year-old made a failed bid to succeed Nelson Mandela as president in 1999, before becoming a wealthy businessman and then returning to politics.
Cosatu does not have voting power in the ANC, but boasts over a million members.
"We shall work to lobby and influence the ANC structures to support comrade Cyril Ramaphosa," said Ntshalintshali.
Among the other names in the running to succeed Zuma are African Union Commission chairwoman Nkosazana Dlamini-Zuma, who is Zuma's ex-wife, and ANC treasurer-general Zweli Mkhize.
Two weeks ago, he survived a motion of no confidence after a public watchdog raised accusations over his relationship with the Guptas, a business family accused of wielding undue political influence.
Zuma's presidential term expires in 2019.