Power comes any way you can get it. Says Graca Michel, the only woman in the world who has been married to two country presidents: “My weakness is, I’m attracted to strong people — people who challenge me. People who are better than myself.”

For the former First Lady twice over, whom I interviewed at a Fortune Most Powerful Women breakfast at the Global Forum in Cape Town, the two “strong people” in Machel’s marital life are Nelson Mandela, her current husband and former president of South Africa, and Samora Machel, the late president of Mozambique. “It happened,” said Machel, as if those remarkable connections came randomly.

They did not happen randomly, of course. Machel’s dramatic course — marrying Mandela, who spent 27 years in prison during apartheid, after she lost her first husband in a plane crash — seems almost predestined by her dramatic personality.

Machel is, as the 100 women leaders who came to the breakfast saw, one of the more passionate and purposeful Presidential wives the world has known. She’s highly accomplished in her own right, a former Minister of Education and Culture in Mozambique and now a prominent advocate for women and children’s rights. Which makes it all the more surprising that Machel views power quite warily. “Power — it frightens me,” she told the group.

Power, to Machel, is about “enabling” and networking “from the ground up,” she told me when I asked her to define the word. Even as she’s working hard these days to encourage women to move into top jobs in companies — and some say, if she had followed a different path, she might have risen to President of Mozambique — Machel insists that she doesn’t want No. 1 status for herself.  “I’ve been very close to it,” she said about power. “And I know how nasty it can be.”