U.S. first lady Michelle Obama (L) and former first lady Laura Bush participate in the "Investing in Our Future" forum at the U.S.-Africa Leaders Summit in Washington Aug 6, 2014. [Photo/Agencies]

"I was aware when George ran for president that you're always going to be characterized in a way that you aren't," she said. "And so I don't think it was any big surprise to me. That doesn't make it any less hurtful. But on the other hand, I think anyone who's in a leadership position of any sort knows you're going to be criticized and a target, really, for criticism."

First ladies have an advantage other political figures do not, she noted.

"We"re elected by one man," she said.

"Right, right," Obama said.

"And you can't be fired," Roberts pointed out.

"Can't be fired,"Obama said.

"We certainly hope not," Bush added.

"I guess we'll see," Obama joked.

But Obama said she was determined to use the last two years of her husband's tenure to maximum advantage.

"We can't waste this spotlight," she said. "It is temporary, and life is short, and change is needed. And women are smarter than men."

Distributed by The New York Times Syndicate.