President Cyril Ramaphosa on Thursday said the ANC had emerged from "a very dark period" under his predecessor Jacob Zuma but would bounce back to win next year's election.
Ramaphosa, who came to office in February after Zuma was ousted by the ANC, admitted that many supporters had abandoned the party Nelson Mandela led to power in 1994 when apartheid rule ended.
But he said the party was tackling corruption problems and would win back voters after its worst election showing in local polls in 2016.
"We are moving from a very dark period of our recent history," Ramaphosa told foreign correspondents in Johannesburg. "The ANC will win, it is just a question of what percentage," he said.
"The shine that had been tarnished is coming back and people are realising this. We are in a new period now - we are no longer in a period where we were just sliding downwards," Ramaphosa said.
"Many people are looking anew at the ANC. They have a sense that we are now beginning to deal with corruption."
He confirmed that he would give evidence to a judicial commission of inquiry into alleged corruption under Zuma.
"I will be going to give an account to the commission about what I knew and what I didn't know," Ramaphosa said.
South Africa is due to hold a general election between May and August next year.