* ANC will win less of the vote than in 2009
* Discontent among poor blacks rising
* Opposition EFF, DA chip away at ANC voter base
* Protests against poor government services (Adds details, quotes, context)
By Helen Nyambura-Mwaura
JOHANNESBURG, Feb 7 (Reuters) - South Africa will go to the polls on May 7, President Jacob Zuma announced on Friday, with his African National Congress likely to easily extend its two-decade rule, despite rising discontent among its poverty-stricken grassroots supporters.
Zuma himself has lost popularity amid allegations of using public funds for private purposes, and the announcement of the election date came as violent demonstrations by residents in largely black townships, against poor government services, spread.
The African National Congress (ANC), which spearheaded the fight against apartheid, should retain the die-hard loyalty of an older generation whose memories of the apartheid system that discriminated against non-whites remain fresh. That should enable the ANC to win the vote with a comfortable majority, giving Zuma another five-year term in office.
But the movement which has been in power since the end of white minority rule in 1994 faces charges of largely failing to lift millions of blacks out of grinding poverty.
Underscoring the volatile atmosphere which has engulfed several townships, hundreds of youths danced and sang in Hebron, a township some 30 kilometres north of the capital Pretoria on Friday, ripping out street signs, lighting tyre barricades and littering roads with boulders and rubble.
"People are never going to vote for the ANC because they are so angry," said Jerry Tlou, 26, outside a Pakistani-owned general store in Hebron, which had just been looted by rioters.
"The ANC makes all these promises but they can't deliver. No water, no electricity, they can't fix the roads. I am going to vote for the DA," Tlou, who is unemployed, said in reference to the opposition Democratic Alliance.
Unemployment in South Africa is running at around 25 percent and growth in Africa's biggest economy has slowed sharply to about 2 percent in 2013, disrupted by the global slowdown and labour unrest that has frequently halted production in the mainstay mining and auto sectors.
The ANC will probably also fail to attract many of the "born free" voters, or South Africans born after the end of apartheid, as young blacks are not overly impressed by its liberation movement credentials.
The Democratic Alliance is the main opposition party but its drive to shed its image as a party that champions mainly white interests suffered a blow this month when a deal to merge with the Agang party and make prominent anti-apartheid activist Mamphela Ramphele the DA's first black presidential candidate collapsed.
ZUMA UNDER FIRE
Twenty four million South Africans have already registered to vote on May 7.
"We have worked hard to build a peaceful and stable South Africa from the ruins of apartheid violence, divisions and hatred," Zuma said in a brief statement announcing the election date on Friday. "Let us make this a vibrant, robust, exciting, peaceful and most successful election, and maintain our track record of successful elections."
But the ANC's credibility has been undermined by its management of the economy and its inability to soothe tensions in the platinum belt, where miners are angry about their lack of economic progress two decades after the end of apartheid.
Zuma, who has also come under fire for allegedly using $21 million of public money for a "security upgrade" to his private home that included a swimming pool, was booed and jeered at the funeral of revered former president Nelson Mandela in December.
The radical Economic Freedom Fighters (EFF), led by expelled former ANC youth leader Julius Malema, is tapping into the simmering discontent to advocate nationalisation of mines and the seizure of white-owned land.
Formed in 2013, the EFF is the latest in a scattering of new political groupings that have emerged recently to try to challenge the ANC. Although still very young, the party is gaining traction with young South Africans who often sport red T-shirts and berets, like Malema, whose red beret has "Commander-in-Chief" embroidered on it.
The ANC will probably win just 56.2 percent of the vote this time, compared with 65.9 percent in the last election in 2009, said Nomura International analyst Peter Attard Montalto.
"Demographics are nibbling away at the "liberation debt" owed to the ANC combined with increasing dissatisfaction with delivery and new choices of party," Montalto said in a note. (Additional reporting by Ed Cropley in Hebron; Editing by Stella Mapenzauswa and Susan Fenton)