“There has never been anything like the Clinton Global Initiative,” he said, “where you’ve raised over $100 billion worth of stuff that helped 43 million people in 180 countries.”

Mr. Clinton spoke to NBC News while in Africa on a tour of some of the foundation’s projects.

“There is no doubt in my mind that we have never done anything knowingly inappropriate in terms of taking money to influence any kind of American government policy,” he said. “That just hasn’t happened.”

He said he might step down from the foundation if Mrs. Clinton is elected but said he won’t stop giving paid speeches.

“I gotta pay our bills,” he said. “And I also give a lot of it to the foundation every year.”