“Her speech was very long and inappropriate for that occasion,” said Vivian Creighton Bishop, a public official in Columbus, Ga., who supports Mrs. Clinton.

Mrs. Obama has also had to learn to tamp down her sometimes biting humor because it too often leaves Mr. Obama as the punch line. (It has been a long time since she has talked publicly about her husband of 15 years being smelly in the morning, as she told Glamour magazine, or forgetting to put away the butter.)

“What I’ve learned is that my humor doesn’t translate to print all the time,” she said in the interview. “But usually when I’m speaking to a group, people understand what I’m trying to say, they get the humor, they understand the sarcasm, they get the joke.”

Her audiences do laugh. Talking about how long it took her and Mr. Obama, 46, to pay off their student loans (they did so only in the last couple of years), she told a church audience in Cheraw, S.C., “I’m still waiting for Barack’s trust fund.” They cackled. She continued: “Then I heard Dick Cheney was supposed to be a relative! Thought we might be in for something here.”

On some occasions, Mrs. Obama’s straight talk has also made it necessary for the campaign to explain her remarks. In the case of “Good Morning America,” campaign officials pointed out that in an unbroadcast portion of the interview, Mrs. Obama later acknowledged that as a good Democrat, she would need to support Mrs. Clinton if she were the nominee.

Mrs. Obama’s nickname inside the campaign is “the closer” because she is skilled at persuading undecided voters to sign pledge cards. But as a smooth orator, she is also known as a connector, volunteering her own life lessons from working-class roots and discussing her confrontation with a culture of low expectations.

She has been transparent about more mundane things, too, like leaning on her mother for child care while she is on the road.