Michelle Obama: I rarely visit West Wing

First lady Michelle Obama is making something very clear: She doesn't get involved in presidential policy.

"I rarely step foot in the West Wing," Mrs. Obama told ABC's Nightline. "In fact, people are shocked when they see me there."

Mrs. Obama is campaigning for her husband. She also directs special projects, including efforts to reduce childhood obesity and to help military families.

But big decisions are left to her husband and others, Mrs. Obama told Nightline anchor Cynthia McFadden.

"I rarely walk in that office because the truth is he's got so many wonderful advisers," she said. "He's got a phenomenal Cabinet. He's got people who are in the trenches on these issues every single day and I'm kind of stepping in and out and I've got my own set of issues.

"So I don't even have the kind of expertise and the time to be able to provide the kind of advice and guidance that he's already getting."

Some past first ladies, from Nancy Reagan to Hillary Clinton, have been accused of over influencing presidential decisions.

Mrs. Obama says she does sometimes discuss issues with the president in private -- but not always.

"In a job like this, the last thing the president of the United States needs when he walks in the door to come home is someone drilling him and questioning him about the decisions and choices that he's made," Mrs. Obama said. "There are definitely times when I may feel something, but I'll hold back because I know he'll either get to that on his own or it's just not time."