POLOKWANE, South Africa — The African National Congress lurched toward a leadership vote yesterday, a usually smooth, private process slowed by a bitter public rivalry that had delegates contesting even how the votes would be counted.

Late yesterday — a day later than expected — President Mbeki and Jacob Zuma were formally nominated for party president, with voting by some 4,000 delegates to start Tuesday. Mr. Zuma, a former guerrilla fighter backed by the left, was expected to win, putting him in line to run for, and likely win, the presidency of South Africa in 2009.

Mr. Mbeki has faced sharp rejection during the party congress, with delegates calling for a change from his aloof manner and what some say is his failure to satisfy a black majority still awaiting housing, jobs and services 13 years after the end of apartheid. The divide has been played out so far in debates over procedural matters. The ANC Youth League, for instance, proposed that ballots in the leadership race be hand counted, expressing skepticism about computer balloting set up by a party election committee seen as close to Mr. Mbeki.

An ANC spokesman, Smuts Ngonyama, said a hand count had been agreed to in order to avoid the “specter of mistrust.”

During the decades it was an underground movement fighting apartheid, the ANC took pride in presenting a united front, and the top party post hadn’t been publicly contested in 55 years. That makes what elsewhere might be seen as the typical hurly-burly of democracy seem shocking.

As the conference began Sunday, delegates loyal to Zuma booed leaders seen as Mbeki allies, carried pictures of Zuma despite a ban on partisan displays, and called for the removal of national chairman Mosiuoa Lekota.

Mr. Zuma’s supporters broke into the anti-apartheid song, “Bring me my machine gun,” which has become his anthem, as soon as Mr. Mbeki finished an address Sunday.