Mr. Zuma faces 16 charges in the arms case, including corruption, fraud, racketeering and money laundering. Lawyers representing Mr. Zuma, who used legal maneuvers and the power of the presidency to avoid prosecution, had hewed to a strategy of delaying his trial as long as possible — what analysts have called the “Stalingrad strategy.”

Mr. Ramaphosa has said that, according to a longstanding agreement between party leaders and Mr. Zuma, who will turn 76 next week, the state will pay for his legal fees because the case relates to actions taken when he was in government.

Mr. Ramaphosa has said that, under the agreement, Mr. Zuma will have to reimburse the state if he eventually loses the case. But the deal effectively gives Mr. Zuma unlimited access to legal representation and raises the possibility that his case will be tied up in the courts for years.

Opposition parties are suing to force Mr. Zuma to pay back his legal fees, and to block the government from paying future ones. The government says it has already spent $1.3 million on Mr. Zuma’s legal defense, though opposition parties say the real amount is several times more.

The dispute over the fees represents a larger problem for the governing party, the African National Congress, or A.N.C., which must determine how strongly to back Mr. Zuma during his corruption trial. Mr. Ramaphosa and his allies have made fighting corruption a priority before national elections scheduled for 2019.

But they cannot afford to completely jettison Mr. Zuma, who remains popular among many A.N.C. followers, especially in his home province, KwaZulu-Natal. The former leader was recently deployed to KwaZulu-Natal, the province with the biggest number of A.N.C. supporters, to drum up support during a voter-registration drive.