When then-Sen. Barack Obama was considering running for president, he asked his skeptical wife, Michelle, what it would take for her to support the effort. As she told “60 Minutes” in 2007, Michelle Obama insisted that her husband quit smoking as a precondition for a White House run. The senator agreed. But nicotine, as so many Americans know, isn’t easy to shake. Last June, Mr. Obama called himself a former smoker but said he sometimes slips up and sneaks a cigarette away from his family and the White House. He said he is “95 percent cured.