Jacob Zuma’s political career could have ended when he was forced to resign six years ago as South Africa’s president over corruption allegations.

Or it could have ended when he was criminally charged for taking bribes, or when he was indicted on rape charges, or when he went to jail for contempt of court, or when he was suspended from the African National Congress, South Africa’s long ruling governing party.

But Mr. Zuma, 82, has improbably bounced back after every threat to his political survival, and now has significant power to determine who will lead the country.

The political party that Mr. Zuma began six months ago — umKhonto weSizwe, or M.K. — finished third in last week’s national election, upending South Africa’s political landscape. The showing helped to bring about the stunning collapse of the party he once led — the African National Congress, or A.N.C., which failed to win an outright majority for the first time since the country’s democracy began in 1994.

Mr. Zuma is positioned to achieve what analysts and political rivals say they believe his return to politics is really about: punishing an A.N.C. that he believes turned against him, and particularly President Cyril Ramaphosa, his former deputy.

“We will take back our A.N.C.,” Mr. Zuma said on Monday, addressing supporters in downtown Johannesburg.