JOHANNESBURG — A South African court on Tuesday ruled that former president Jacob Zuma can stand in the upcoming general elections, overturning a decision by electoral authorities to bar him over a contempt conviction.

In a surprise verdict, the electoral court ruled in favor of the 81-year-old who is leading uMkhonto we Sizwe, or MK, a new opposition party that has become a potential upsetter in the elections.

"The decision of the Electoral Commission … is set aside," the court wrote in a ruling seen by Agence France-Presse.

It did not provide an explanation of how the verdict was reached.

South Africa will hold the national and local government elections on May 29.

South Africa's general elections are expected to be the most competitive since the advent of democracy in 1994 and Zuma's presence in the campaign could prove a key factor.

Banking on his popularity, MK is expected to cut into the vote share of the embattled ruling African National Congress, or ANC, the former president's former political home.

This could see the ANC's vote share drop below 50 percent for the first time since 1994.

Short of a parliamentary majority, it would be forced to seek coalition partners to remain in power.

MK hailed the ruling as a "triumph" over what it said were ANC-led efforts to marginalize it.

"This victory extends beyond president Zuma and the MK Party as it symbolizes a victory for every South African who believes in fairness, democracy, and the inviolable right to elect leaders of their choice, free from undue interference," it said.

The Electoral Commission said it had taken note of the decision but asked the reasons for it.

"Naturally the commission is taking legal advice … and will chart a way forward based on such advice," it said.

The Electoral Commission had excluded Zuma from the race, saying the constitution barred anyone convicted and sentenced to more than 12 months' imprisonment.

Zuma was sentenced to 15 months in jail in June 2021 after he refused to testify before a panel probing financial corruption and cronyism during his presidency.

His lawyers argued the sentence did not disqualify him as it followed civil rather than criminal proceedings and it had been shortened by a remission.

Zuma was freed on medical parole just two months into his jail term.

"If the masses want me to be president, what's going to stop them?" an upbeat Zuma told supporters, after Monday's hearing.

Some opinion polls put MK at above 10 percent nationwide, a share that would make it the third or fourth political force behind the ANC and the liberal Democratic Alliance.

Tensions between the ANC and MK have run high in recent months.

The ANC has unsuccessfully tried to have the new party disqualified and has taken it to court to stop it from using the MK name, alleging intellectual property theft.

Last week the MK leader appeared in court accused of inciting violence for saying that massive riots would erupt if the MK was not allowed to run.

The Electoral Commission is expected to publish the final candidate list on Wednesday.