Joe Biden, on the campaign trail, explained that his wife's desire for the highest degree was in response to what she perceived as her second-class status on their mail.

“She said, 'I was so sick of the mail coming to Sen. and Mrs. Biden. I wanted to get mail addressed to Dr. and Sen. Biden.' That's the real reason she got her doctorate,” he said.

Amy Sullivan, a religion writer for Time magazine, said she smiled when she heard the vice president's wife announced as Dr. Jill Biden during the national prayer service the day after President Obama's inauguration.

“Ordinarily when someone goes by doctor and they are a Ph.D., not an M.D., I find it a little bit obnoxious,” Sullivan said. “But it makes me smile because it's a reminder that she's her own person. She wasn't there as an appendage; she was there as a professional in her own right.”