![Nelson Mandela, Barack Obama](https://ibw21.org/wp-content/uploads/2018/07/nelson-mandela-barack-obama-910x512.jpg)
By Olivia B. Waxman, TIME — When Barack Obama delivers the 16th Nelson Mandela Annual Lecture in Johannesburg on Tuesday, to mark this week’s centennial of the late anti-apartheid champion Nelson Mandela’s birth, the moment will be a deeply personal one for the former president. His speechwriter Ben Rhodes has said that Obama considers it to be the most important speech since leaving office, and Obama has written that his political awakening…