But there was something darker and sharper lurking just below the surface, in Obama’s facial expressions, body language, and mocking tone of voice: Not to put too fine a point on it, but the president has a mean streak.

“He does have a very biting side to him, which he inherited from his mother,” said Pulitzer Prize-winning biographer David Maraniss, whose much-anticipated Barack Obama: The Story will be published next month. The late Ann Dunham “could be very sarcastic, but she never addressed it to people who were vulnerable,” Maraniss continued. “Obama has got that style that comes out when he’s in combat or competitive.”…

“It’s his use of mockery,” Frank said. “He has a way of putting people down that is somewhat reminiscent—I hate to say this—of George Bush.” Frank recalled a presidential press conference in October 2003, when Bush famously insulted Associated Press radio correspondent Mark Smith by saying that he had “a face for radio.” When Smith replied, “I wish I could say that was the first time you told me that, sir,” noting that Bush had said it once before in front of Smith’s wife, Bush gloated, “The first time I did it to a national audience, though!”

Frank explained: “Everybody has sadistic impulses, and usually they come out when people are feeling cornered. Bush had no filters on his sadism. He just attacked. Obama processes his sadism to the point where he gets somewhat more acceptable. It’s actually mocking a person, like Romney, but it’s also mocking his ideas … The eye-rolling is something his mother did. It’s a way of putting someone else down without ever being directly confrontational.”