* ANC shares power after election slump

* Party of Mandela teams up with white-led DA

* Tie-up worries many Black ANC supporters

JOHANNESBURG, June 15 (Reuters) - For the first time since Nelson Mandela negotiated an end to white minority rule, former sworn enemies are coming together in South Africa under a pledge to overcome ideological differences for the good of the nation.

President Cyril Ramaphosa has said the seismic political shift is a response to voters' demands for solutions to deepening woes - from sky-high unemployment and economic torpor to corruption and failing infrastructure.

But the prospect of the African National Congress - the liberation movement that freed the country from apartheid - governing alongside the white-led Democratic Alliance (DA), does not sit well with many Black South Africans.

"The ANC is siding with the enemy of progress," said 25-year-old ANC voter Nathi Mboniswa, who worried his party risked compromising its values in a partnership with the DA.

In a disastrous showing in elections last month, angry voters dismantled the ANC's 30-year-old majority. With little choice but to share power, Ramaphosa announced he would form a government of national unity open to parties across South Africa's diverse political landscape.

But the electoral maths dictated the ANC would need to bring in at least one of its biggest rivals - the business friendly DA, the radical left Economic Freedom Fighters (EFF) or populist uMkhonto we Sizwe.

The latter two refused to participate in a government that included the DA.

Following Ramaphosa's re-election by lawmakers on Friday, EFF leader Julius Malema used his allotted time for congratulations to instead blast the tie-up with the DA.

"History will judge you and judge you harshly," he said. "This is not a government of national unity. This is a grand coalition between the ANC and white monopoly capital."

The DA, which wants to abolish some ANC Black empowerment policies, rejects any accusations it represents the country's wealthy whites, saying its economic reforms would benefit all South Africans.

FOR THE LOVE OF THE PEOPLE

After three decades working to break the ANC's unchallenged grip on power, the DA - South Africa's second largest party - emerged from the coalition talks in triumphant mood.

"The DA takes this historic step forward out of our deep and abiding love for the people of this country," its leader John Steenhuisen said in a televised address, pledging to scale up the successes it recorded in its strongholds.

In contrast to the rest of the country, Western Cape province, which the DA has controlled since 2009, has done measurably better, with lower unemployment, less severe power cuts and higher investment.

Convincing sceptics, however, won't be easy.

In a country with a painful racial history where white South Africans make up just 7% of the population, the DA has struggled to prove it reflects the aspirations of all.

The predominantly white composition of its national leadership has not helped.

"The melanin-quotient of the DA leader is the least significant aspect of this historic agreement," Helen Zille, one senior DA official, wrote on X on Friday, criticising a focus by international media on Steenhuisen's race.

But the DA's free-market, small government ideology also worries many in South Africa, where 24 million - more than a third of the population - survive off welfare.

Vows to end an ANC-established racial quota system for employers despite the still lingering economic effects of apartheid-era discrimination have also drawn criticism.

"I hope that the ANC can ensure that the progressive policies of the left are advocated for," said Kabelo Phungwayo, a 22-year-old ANC supporter.

'WIPED OUT'

The ANC leadership has been at pains to assuage such concerns among its ranks.

Secretary-General Fikile Mbalula has said that details of how the coalition will operate have yet to be finalised. He has also acknowledged that if the ANC caved in to all of the DA demands it would be "dead".

"We must be a revolutionary party," he said on Friday. "We will be wiped out if we lose the people."

All sides continue to call the new political bloc a government of national unity despite the coalition's two other members - the Inkatha Freedom Party and Patriotic Alliance - being relative minnows.

"The ANC is effectively running away from taking responsibility for getting into a coalition with the DA. So they then find the language to sanitise what is going on," said Lukhona Mnguni of Rivonia Circle, a Johannesburg-based think tank.

The best way of silencing criticism and putting to rest any misgivings about partnering with the DA, however, will likely be through acts.

Last month's polls made clear that even many of the ANC's own supporters have grown weary of South Africa's years of decline and are clamouring for something new.

"This coalition marks the beginning of a new era where South African leaders put their differences aside," said Sandra Sholayan, a 56-year-old communications manager from East London, who voted for the ANC.

"Together we can do more." (Additional reporting by Nellie Peyton, Sfundo Parakozov and Siyabonga Sishi in Johannesburg, Wendell Roelf in Cape Town and Johnnie Isaac in East London; Editing by Silvia Aloisi and Kirsten Donovan)