Johannesburg (CNN) Despite years of corruption allegations, a sluggish economy and sustained electricity blackouts, South Africa's ruling ANC looks set to win a substantial majority in a critical national election.

With more than 90% of the vote counted, the ANC shows a strong lead with just over 57% of the national vote, according to partial results released by the country's electoral commission.

While the ruling party looks set to maintain its grip on power for the next five years, the results show that voter support for the ANC -- the party of Nelson Mandela -- which has governed since the fall of apartheid in the mid-1990s, is dwindling. The falling support means that it will be harder for the weakened party to enact its agenda -- including bolstering the flagging economy.

The party looks set to dip below the psychological barrier of 60% support -- since the end of the apartheid regime in 1994, the ANC's share of votes in national elections has never fallen below 60%, according to the commission.

In the previous election, in 2014, the ANC won with 62% of voter support. The election year before that -- 2009 -- the party won 66% of the vote. In 2004, it got close to 70% of the vote.

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