It's not unusual to see a reporter or staffer smoking on the White House grounds, but one person who won't be found puffing away is President Obama.

Just a few years ago, when pushing for passage of the Affordable Care Act, he admitted that permanently kicking the addictive habit was a struggle for him. But quit he did, and now everyone knows why: the world's most powerful man is afraid of First Lady Michelle Obama.

In a conversation caught on an open mic, United Nations official Maina Kiai, who still indulges in nicotine "sometimes," asked Obama if he does, too.

"No, no," the president grinned. "I haven't had a cigarette in probably six years. That's because I'm scared of my wife."

In an interview with iVillage last year, the first lady said that the president made the decision to quit because "he didn't want to look his girls in the eyes and tell them that they shouldn't do something that he was still doing."

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(Photo: CNN)