From the LA Times:
In 2007, at 55, Jill Biden did earn a doctorate—in education—from the University of Delaware. Since then, in campaign news releases and now in White House announcements, she is "Dr. Jill Biden." This strikes some people as perfectly appropriate and others as slightly pompous, a quality often ascribed to her voluble husband….
Some second ladies, as vice presidents' wives are called, have been accomplished professionals. Marilyn Quayle is a lawyer, but she did not practice while her husband, Dan, was in office. Lynne Cheney, Jill Biden's immediate predecessor, is a novelist who earned a doctorate in English with a dissertation titled "Matthew Arnold's Possible Perfection: A Study of the Kantian Strain in Arnold's Poetry." She goes by Mrs. Cheney….
But Biden is thought to be the first second lady to hold a paying job while her husband is in office….
As a Ph.D. in my own right, let me say that people, including medical doctors, podiatrists, veterinarians, dentists, and Ph.D.s, who insist on being called doctor are usually painful to be around. I do enjoy the special pleading Dr. Biden's case has brought forth:
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 PhD, not an MD, 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."
Yes, it's quite a reminder that the spouse of a politician is a person in her own right. The last one who really was, if I remember correctly, was Howard Dean's wife, who refused to campaign with her husband.