Deputy President Cyril Ramaphosa won the backing of South Africa’s biggest labour federation to succeed President Jacob Zuma as leader of the governing ANC.

The decision by the Congress of South African Trade Unions, a key ally of the ANC, came after an “intense and robust debate”, Cosatu secretary-general Bheki Ntshalintshali told reporters in Johannesburg.

Ramaphosa, 64, and Nkosazana Dlamini-Zuma, Zuma’s 67-year-old ex-wife whose time as chairwoman of the African Union Commission ends in January, are seen as the front-runners to succeed Zuma at the ANC’s elective conference due in December next year. The leader of the party, which has a majority in parliament, will probably become president in a national vote in 2019.

Ramaphosa, a lawyer who co-founded the National Union of Mineworkers, helped negotiate a peaceful end to apartheid and draft South Africa’s first democratic constitution. He lost out to Thabo Mbeki in the contest to succeed Nelson Mandela as president in 1999 and went into business, securing control of the McDonald’s franchise in South Africa and amassing a fortune before returning to full-time politics in 2012 as ANC deputy president.

The rand reversed losses, gaining as much as 0,8% against the dollar after the announcement, and was at R14,12/$ at 11.51am in Johannesburg on Thursday.

Other potential contenders could be Zweli Mkhize, 60, the ANC’s treasurer-general and former premier of KwaZulu-Natal province, and Baleka Mbete, 67, the speaker of parliament and ANC chairwoman.

While Cosatu’s endorsement will boost Ramaphosa’s chances of becoming president, the succession race remains wide open, said Roger Southall, an emeritus professor of sociology at the University of Witwatersrand in Johannesburg.