Very early counts in South Africa’s national election put the long-ruling African National Congress at just over 42% of the vote, raising the possibility that it might lose its majority for the first time since it swept to power under Nelson Mandela at the end of apartheid in 1994.

With only just over 16% of votes counted and declared, it was only a partial picture after Wednesday’s election. The final results of a vote that could bring the biggest political shift in South Africa’s…