IN 2011, the British historian Stephen Ellis published a paper concluding that Nelson Mandela had been a member of the South African Communist Party — indeed, a member of its governing Central Committee. Although Mandela’s African National Congress and the Communist Party were openly allied against apartheid, Mandela and the A.N.C. have always denied that the hero of South Africa’s liberation was himself a party member. But Ellis, drawing on testimony of former party members and newly available archives, made a convincing case that Mandela joined the party around 1960, several years before he was sentenced to life in prison for conspiring to overthrow the government.

Does it matter?...

Mandela’s Communist affiliation is not just a bit of history’s flotsam. It doesn’t justify the gleeful red baiting, and it certainly does not diminish a heroic legacy, but it is significant in a few respects....

Perhaps the most important and lasting personal effect of the South African Communist Party on Mandela was that it made him, or helped make him, a committed nonracialist. The A.N.C. in its formative years admitted only blacks. For a long time, the Communist Party was the only partner in the movement that included whites, Indians and mixed-race members. That relationship is one of the main reasons Mandela cited for his rejection of black nationalism and his insistence that multiracialism remain at the heart of the A.N.C. ethic....